Any compromises agreed with Russia to end its invasion will need to be voted on in a referendum, Ukrainian President Volodymyr Zelenskyy has said.
Issues of concern could include security guarantees offered in lieu of NATO membership, and areas occupied by Russia forces, such as Crimea.
Ukrainian citizens will "have to speak up and respond to this or that form of compromise", Mr Zelenskyy said.
Potential compromises "will be the subject of our talks and understanding between Ukraine and Russia", he said in comments published by Ukrainian public broadcaster Suspilne.
Earlier, in a sign of the continuing fierce resistance to the invasion, Ukraine refused to give up the besieged city of Mariupol, saying there will be "no talk of any surrender".
On a day when Russian forces targeted another port city for the first time - Odesa - and intensified attacks on Kyiv, Ukraine's deputy prime minister also said there would be no "laying down of arms".
Residents refused Moscow's offer of "safe passage" out of Mariupol after a deadline of 5am was set.
In the capital, Mayor Vitali Klitschko announced a 40-hour curfew. It began at 8pm local time on Monday night and runs until 7am on Wednesday.
People are advised to "stay at home, or in shelters when the alarm sounds".
Mr Klitschko said he had imposed the curfew because of the "likelihood of more shelling".
Map showing Russian controlled areas as of 21 March 2022
The Russian advance on Kyiv appears to be in trouble, however.
According to British military intelligence, Vladimir Putin's forces advancing from the northeast have stalled and the bulk remain more than 15 miles (25km) from the centre of the capital.
"Heavy fighting continues north of Kyiv," the UK's Ministry of Defence said in its latest update.
"Russian forces advancing on the city from the northeast have stalled. Forces advancing from the direction of Hostomel to the northwest have been repulsed by fierce Ukrainian resistance. The bulk of Russian forces remain more than 25 kilometres from the centre of the city."
But Kyiv remains "Russia's primary military objective" and it is "likely to prioritise attempting to encircle the city over the coming weeks", the MOD said.
Ukrainian forces are also holding on to the eastern city of Kharkiv.
As the conflict continues, Ukraine's defence minister, Oleksii Reznikov, has accused Moscow of "committing a real act of genocide" and said Russian forces had killed more than 150 children, destroyed more than 400 schools and nurseries and 110 hospitals.
He reiterated calls for NATO to establish a no-fly zone over Ukraine and demanded tougher sanctions against Russia to "stop the evil" and "state terrorism".
At least eight people have been killed by Russian shelling in the capital, with a shopping centre, residential buildings offices and a gym among the places hit in the Podil district, police said.
"We saw a number of bodies laid out on the pavement outside the mall," said Sky's Alex Crawford.
Crawford added: "This is what life is like for those living in the city right now. An attack can come out of nowhere, any time, any place... they're using long-range rocket strikes instead to terrorise and kill."
But shortly afterwards, photographs began circulating on the internet which appeared to show the shopping mall with military vehicles parked underneath. It is not clear how recent these photographs are or their origin.
Authorities in Odesa accused Russian forces of targeting civilians after carrying out a strike on homes in the outskirts of the city - the first such attack on the Black Sea port city.
"These are residential buildings where peaceful people live," Mayor Gennadiy Trukhanov was quoted as saying. "We will not leave Odesa and we will fight for our city."
The city council said there were no casualties although the shelling caused a fire.
In the early hours residents heard "large bangs" coming from the Black Sea, where there has been a Russian naval build-up for the past week, said Sky correspondent Nick Martin.
Shrapnel from the shelling peppered holes into buildings, including apartments, and smashed windows - sending shards of glass cascading down on to the streets of the city and so-called jewel of the Black Sea.
Russia says it has docked a large, landing support ship, the Orsk, in the occupied Ukrainian port of Berdyansk, 45 miles (70km) southwest of Mariupol on the Sea of Azov.
"It is hard to overestimate the possibilities of using this port," said the website of the Russian armed forces news outlet Zvezda (Star). "Now the southern flank of the special operation can receive everything necessary at any time, including equipment and ammunition."
The website said 10 such ships - each can carry up to 20 tanks or 40 armoured personnel carriers - are part of what Moscow has called its "special military invasion" in Ukraine.
Mariupol, which sits between Russian military bases in Crimea and the disputed Donbas region in eastern Ukraine, has been surrounded from the outset of the invasion because its capture would allow Russian forces to unite.
Refusing the Kremlin's offer to allow the evacuation of civilians from Mariupol if it surrendered, Deputy Prime Minister Irina Vereshchuk told news outlet Ukrainian Pravda: "There can be no talk of any surrender, laying down of arms. We have already informed the Russian side about this.
"I wrote 'instead of wasting time on eight pages of letters, just open the corridor'."
The Russians have attacked Mariupol almost relentlessly since the start of the Russian invasion of Ukraine on 24 February, with the latest strike being at an art school that was sheltering around 400 people.
Speaking earlier on Monday, Ukrainian President Volodymyr Zelenskyy said: "They are under the rubble, and we don't know how many survived.
"But we know that we will certainly shoot down the pilot who dropped that bomb, like about 100 such mass murderers whom we already have downed."
He has described the siege of Mariupol a war crime and "a terror that will be remembered for centuries to come".
Ukraine has accused Russian forces of bombarding buildings including a maternity hospital, swimming pool and a shopping centre - as well as a theatre where it said people were sheltering last week.
Hundreds of men, women and children were thought to have been in the theatre's basement after their homes were destroyed during the invasion - and the word "children" had reportedly been displayed in large letters at the site, prior to the attack, warning warplanes of those inside.
Aid groups have said food, water, and electricity are running low in the city, with humanitarian access limited by the fighting.
The city's authorities have said at least 2,300 people have died, some buried in mass graves.
Mariupol has been subjected to three-and-a-half weeks of Russian siege and shelling which the Red Cross says has caused "apocalyptic" destruction.
It has, at the same time, been one of the most difficult cities for civilians to leave, with humanitarian corridors rarely in operation, and each side blaming the other for them failing.
Thousands of Ukrainians from Mariupol have been "forcibly deported" to Russia, according to the city council.
Another city to have come under an unrelenting Russian assault is Kharkiv - a short drive from the border with Russia.
Authorities in the eastern city said at least five civilians have been killed in the latest Russian shelling.
Regional police in Ukraine's second-largest city said victims of the artillery attack on Sunday included a nine-year-old boy.
Sky correspondent John Sparks travelled with the Ukrainian military to the front line on the outskirts of the city and described the "air filled with the deep-sounding boom of tank and artillery fire".
Signs war headed for 'stalemate rather than negotiated solution'
The war is headed for "a long, grinding campaign" where the Russians "try and smash one town after another in the hope of breaking the will of the Ukrainian people", former Foreign Office permanent secretary and national security adviser Lord Ricketts has said.
He told Sky News: "I think it is clear the Russians cannot win an outright victory - the Ukrainian resistance has been far too strong for that. We have seen even in Mariupol, after weeks and weeks of smashing that city to pieces, people are not ready to surrender to Russian forces.
"How much more difficult will that be in a massive city like Kyiv? They are clearly stalled, bogged down, all kinds of problems with their logistics and I don't think they are ready yet to declare any kind of a ceasefire negotiation. The positions of the two sides are far too far apart for that.
"I think we are in for a stalemate rather than a negotiated solution."
Ten million people have been displaced by the conflict, including nearly 3.5 million who have fled abroad, according to the UN refugee agency.
The Great Debate airs on Sky News at 9pm on Monday
Russia says it has hit a Ukrainian military facility
Russian air forces hit a Ukrainian army military facility in the Rivne region in the west of the country with cruise missiles, Russia's Defence Ministry said on Monday.
"High-precision air-launched cruise missiles have struck a training centre for foreign mercenaries and Ukrainian nationalist formations," defence ministry spokesman Igor Konashenkov said.
https://news.sky.com/story/ukraine-...raine-refusing-to-surrender-mariupol-12571816
