Half of the US Senate – 25 Republicans and 25 Democrats – have in a rare bipartisan move put forward sanctions that would be imposed on Russia if it refuses to engage in good faith negotiations with Ukraine and respect an eventual peace deal. The lead sponsors of the legislation, the Republican senator Lindsey Graham and the Democratic senator Richard Blumenthal, said: “The sanctions against Russia require tariffs on countries who purchase Russian oil, gas, uranium and other products. They are hard hitting for a reason.”

“The dominating view in the United States Senate is that Russia is the aggressor, and that this horrific war and Putin’s aggression must end now and be deterred in the future,” they said. Companion legislation is being introduced in the House of Representatives, also with the support of both Republicans and Democrats. Backers say it will pass with overwhelming support in both chambers if Congress’s Republican leaders allow a vote, but there was no immediate word on when a vote might take place.

It comes as both legislators and the Trump administration appear to recognise the US needs to put pressure on the Kremlin just as it has on Kyiv. US national security council spokesperson James Hewitt said: “There is a deep frustration with the Russian government over negotiations. President Trump was clear he will consider imposing secondary sanctions on all oil coming out of Russia if they are not serious about bringing this conflict to a peaceful resolution.”

The Reuters news agency reported that officials inside the White House and state department have acknowledged Vladimir Putin is actively resisting peace efforts and are discussing how to push Russia closer to a deal. The Kremlin on Tuesday complained that it cannot accept US ceasefire proposals in their current form. On Monday, European foreign ministers lined up to call out Vladimir Putin for, as top EU diplomat Kaja Kallas put it, “playing games and not really wanting peace”.

Speaking in Ukraine alongside Germany’s visiting foreign minister, Annalena Baerbock, Volodymyr Zelenskyy urged the US to ramp up sanctions on Russia after what he said were violations of a ceasefire on energy infrastructure. The Ukrainian president said the US had told Ukraine privately that it had seen the Russian violations. Russia has itself accused the Ukrainians of continuing to strike energy infrastructure, something Kyiv denies. Zelenskyy has for weeks declared Ukraine ready for an unconditional general ceasefire.

Ukraine will hold in-depth talks on Friday with a small group of foreign countries about contributing forces to a contingent that would act as a security guarantee for Ukraine, Zelenskyy said on Tuesday. The contingent would include a land component, an air component and a presence at sea. Britain’s prime minister, Keir Starmer, has said British, French and Ukrainian military leaders will meet in the coming days to build on “real momentum” in efforts to boost Ukraine’s security. Britain and France are leading efforts to form a “coalition of the willing” of Ukrainian allies.

Russia’s advance in Ukraine has slowed for a fourth month, according to the Agence France-Presse news agency, which analysed data from the Institute for the Study of War.

People in Britain working with Russian authorities in any way will have to go on the UK’s foreign influence register by 1 July or face five years in jail. The British Home Office minister, Dan Jarvis, told parliament it included “carrying out activity as part of any arrangement” with Russian authorities including government agencies, armed forces, intelligence services and the Moscow parliament. Russian political parties controlled by the Russian government, including the United Russia party, will also need to declare what they are doing before they can carry out activity in the UK.

Polish prosecutors said they had charged a Russian-born Ukrainian with spying on military installations in Poland for Russia’s intelligence services. The 47-year-old man could face from five to 30 years in prison. Since the start of the Russian invasion, 44 people – Russians, Belarusians, Ukrainians and Poles – have been detained in Poland on suspicions of espionage or sabotage.

The value of Russian assets frozen in Switzerland because of Russia’s war on Ukraine has risen by nearly $2bn in the past year to more than $8bn, the Swiss government said on Tuesday. In addition, “14 real estate assets belonging to individuals, companies, or entities subject to sanctions” have been identified, as well as things such as sports cars and luxury cars, aircraft, artworks and furniture. Switzerland, usually neutral, decided four days after Russia invaded Ukraine to align itself with EU sanctions.