Western sanctions on Russia need to be increased, not weakened, in order to bring it to the negotiating table, Sir Keir Starmer has said.

The prime minister accused Vladimir Putin of "playing games and playing for time" after the Russian president demanded that sanctions were lifted before a US-brokered maritime ceasefire is enacted.

"Now is not the time for pulling back or weakening sanctions - now is the time to increase sanctions to get them to the table," Starmer said in Paris, where he is meeting European leaders.

French President Emmanuel Macron, co-hosting Thursday's so-called "coalition of the willing" summit, has suggested a European reassurance force could "respond" if attacked by Moscow.

Starmer said on Thursday that a "framework and a deadline" was needed for Ukraine peace talks.

He said he had agreed with partners at the summit, which hosted representatives from 30 nations as well as the European Union and NATO, that "we must go further now to support the peace process, support Ukraine and increase the pressure on Russia to get serious".

"It means increasing the economic pressure on Russia, accelerating new tougher sanctions, bearing down on Russia's energy revenues, and working together to make this pressure count," he said.

Starmer said that the political mood to find a just and lasting peace in Ukraine was "stronger and broader" than it had ever been, adding that "Europe as a whole has not been this strong and united in a long time".

The UK will chair the next meeting of the Ukraine Defense Contact group, comprised of dozens of countries, to deliver further military aid and "keep Ukraine in the fight", Starmer said.

The prime minister said defence chiefs from the UK, France and Germany would also be meeting in Ukraine, but did not specify a date.

Speaking with Ukraine's President Zelensky earlier, Starmer accused Russia of "continuing to inflict devastating attacks on the Ukrainian people" and said Putin's promises were "hollow".

Zelensky said that everybody at the meeting understood "that Russia doesn't want any kind of peace" and was "dragging out the war, adding that they would discuss security guarantees in the coming weeks and days.

In a post on X, the Ukrainian leader thanked the UK and France for their support and shared a picture of himself and Starmer holding talks, describing the plans as a "coalition of strength for the sake of peace".

"Our unity and joint work in Europe, with the United States, and other partners, can force Russia into peace," Zelensky added.

Russia and Ukraine have accused each other of breaking the terms of a separate, tentative deal to pause strikes on energy infrastructure.

Washington announced the Black Sea deal had been agreed on Tuesday, after holding separate talks with delegations from Ukraine and Russia in Saudi Arabia.

But just hours later, the Kremlin said it would not take effect until sanctions were lifted on Russian banks, producers and exporters involved in the international food and fertiliser trades.

Moscow's demands include reconnecting Russian banks involved in the agrifood trade to the Swift payment system, lifting restrictions on servicing ships under the Russian flag involved in the food trade, and revoking sanctions on the supply of agricultural machinery and other goods involved in food production.

US President Donald Trump said the US government was "looking at" Moscow's request - but the EU said it would not consider removing sanctions before the "unconditional" withdrawal of Russian troops from Ukraine's internationally recognised territory.

Zelensky said on Wednesday he hoped the US - which is not a part of the coalition of the willing - would "stand strong" in the face of Russian demands.

Macron confirmed that European countries had "unanimously agreed" that sanctions against Moscow should not be lifted.

"The time is not ripe to lift sanctions... We need to keep economic pressure up," he said.

The French president said that if a European force protecting a ceasefire in Ukraine came under attack, it would "respond to it".

"If there were again a generalised aggression against Ukrainian soil, these armies would be under attack, and then it's our usual framework of engagement," he said.

"Our soldiers, when they are engaged and deployed, are there to react and respond to the decisions of the commander in chief and, if they are in a conflict situation, to respond to it."

The UK and France are leading efforts to send a force to Ukraine to deter any future Russian aggression in the event of a ceasefire.

Starmer reiterated on Thursday that Parliament should have a say on deploying troops.

European leaders put on a show of unity in Paris. In reality, many have already ruled out sending troops to Ukraine.

Countries including Finland and Poland feel under direct threat from Russia and feel their troops need to protect their own borders. Others fear that deploying soldiers would be a deeply unpopular decision at home.

Italy's Prime Minister Giorgia Meloni, who has repeatedly expressed her scepticism at the Franco-British plan, has been working to put forward an "alternative" option which would see soldiers serve in Ukraine exclusively as part of a United Nations military contingent.

European officials say that under any peace settlement, Ukraine's first line of defence against any future Russian attack would be its own army.

Russian Foreign Ministry spokeswoman Maria Zakharova said a European force in Ukraine would risk a "direct clash between Russia and NATO", state-owned news agency Tass reports.

"London and Paris continue to nurture the idea of a military intervention in Ukraine. All of that is being cloaked under [the guise of] a certain peacekeeping mission," Zakharova said.

She added Russia was "categorically against such a scenario".