Keir Starmer will give a press conference after key meetings with European allies today on protecting any peace in Ukraine.
The PM will gather in Paris with the "coalition of the willing" - a group of leaders prepared to help police a potential peace deal between Moscow and Kyiv.
He is set to update leaders at the Elysee Palace on progress in hammering out peacekeeping plans after 200 military planners met at Northwood in Hertfordshire last week. Military planning has looked at air land and sea forces to protect a ceasefire, including aircraft, tanks, troops, intelligence and logistics capabilities.
Mr Starmer is expected to tell around 30 leaders all countries must come together to support Ukraine to remain in the fight and back US efforts to secure a peace deal. He is set to tell them: "Unlike President Zelenskyy, Putin has shown he’s not a serious player in these peace talks.
"Playing games with the agreed naval ceasefire in the Black Sea despite good faith participation from all sides – all while continuing to inflict devastating attacks on the Ukrainian people. His promises are hollow. The US is playing a leading role by convening the ceasefire talks, President Zelenskyy has demonstrated his commitment repeatedly, and Europe is stepping up to play its part to defend Ukraine’s future. Now Putin needs to show he’s willing to play ball.”
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But Mr Starmer could also face questions on the impact of the Chancellor's Spring Statement when he appears at a press conference in Paris around lunchtime. The DWP's official assessment showed on Wednesday controversial benefit cuts could plunge 250,000 people - including 50,000 kids - into poverty.
A grim analysis published on Wednesday also found poorer households are set to be £500 worse off due to measures in Ms Reeves's Spring Statement. The Resolution Foundation said the bleak economic outlook and benefit cuts will fall disproportionately on lower-income families.
The PM may also be quizzed on Donald Trump's overnight announcement to slap a 25% tariff on car imports to the US from April 2. Speaking on Wednesday, Chancellor Rachel Reeves said the UK government is in "intense negotiations at the moment with our US counterparts" over tariffs.
The talks include "cars and steel and every other type of tariff", she told the BBC. She added: "That's been ongoing since our Prime Minister, Keir Starmer, went to the White House to meet the US president just a few weeks ago. Those talks continue."
Asked if the talks could lead to exemption for UK-based car companies, Ms Reeves replied: "Well, that's what we're working on. We've got a few more days left of those negotiations before these tariffs are due to come in." The US is "rightly concerned about countries that run persistent, large trade surpluses with them", Ms Reeves said, but insisted the UK is "not one of those countries".