The US and its G7 partners have warned Moscow they could expand sanctions and use frozen Russian assets to support Ukraine, as Donald Trump seeks to win over Vladimir Putin to his ceasefire proposal.

After a week in which Kyiv signed up to the 30-day truce but Moscow signalled reluctance to do so immediately, US secretary of state Marco Rubio and his counterparts achieved a degree of unity on Friday by thrashing out a joint statement on possible steps against Russia.

Their communiqué, released after a G7 meeting in Canada, noted that the foreign ministers discussed imposing further penalties if the Kremlin did not fully implement a ceasefire.

Asked about US sanctions, Rubio cautioned that Trump “doesn’t want to do that right now, because he’s in the hopes of attracting people on both sides to a process where we can negotiate peace.”

He added that it was not yet clear whether Russia was playing for time.

“The question is, are we actually moving towards a ceasefire, or is this a delay tactic?” the secretary of state said. “I’m not going to answer that because I can’t characterise that for you right now.”

The G7 statement said ministers had discussed possible measures against Moscow such as “caps on oil prices, as well as additional support for Ukraine, and other means”, notably using revenues from frozen Russian assets.

The G7 froze about €300bn in Central Bank of Russia assets — mostly cash and government bonds — in 2022 after Moscow’s full-scale invasion of Ukraine.

Rubio, who has previously indicated that Kyiv would have to make territorial concessions, signalled on Friday that Moscow would also have to do so.

“I’ve never heard President Trump say that Russia has a right to take all of Ukraine and do whatever they want there,” he said.

He added that Trump’s national security team will convene this weekend after the president’s envoy Steve Witkoff returns from Moscow to examine the Russian position.

Trump said in a post on his Truth Social network that the previous day’s discussions with Putin had been “good and productive”.

Until this week, the new administration has focused on putting pressure on Kyiv to agree a rapid end to the war, but doubts expressed by Putin about an immediate ceasefire have shifted attention to Moscow.

“The ball is now in Russia’s court when it comes to Ukraine,” Canada’s foreign minister Mélanie Joly told reporters on Friday, adding that there was “strong G7 unity” on Ukraine.

One official said the communiqué text on Ukraine had been the subject of tense wrangling overnight. The US argued that strong language could disrupt talks with Russia and it was watered down to reach an agreement, they said.

Kyiv and its allies in Britain and France have been keen to overcome a disastrous meeting last month between Trump and his Ukrainian counterpart Volodymyr Zelenskyy by putting measures against Russia back on the US agenda.

Zelenskyy’s government agreed to Trump’s proposal this week after the US had suspended military assistance and intelligence sharing with Kyiv — both of which Washington now says it has resumed.

By contrast, Putin said he supported a ceasefire but added that “issues” remained that needed to be discussed first.

His reluctance to back the ceasefire proposal comes as Russian forces have made significant advances in the Kursk region, where Ukraine seized more than 1,000 sq km from Russia last summer.

In his Truth Social post Trump claimed the Russian army had surrounded thousands of Ukrainian troops, adding that “I have strongly requested to President Putin that their lives be spared”.

Ukraine’s general staff denied that Ukrainian troops had been encircled and said fighting was still ongoing in the Kursk region.

Putin said on Friday that the Ukrainian troops in Kursk should surrender “to carry out Trump’s appeal” as Zelenskyy dismissed Moscow’s stance on a ceasefire as a stalling tactic.

“The devil is in the details, and they will start offering you details to drag you into a dialogue, delay certain processes and postpone the end of the war”, the Ukrainian president said. He added that he hoped for a “strong reaction” from Trump to Putin’s position.

Zelenskyy also said the issue of Ukrainian territories occupied by Russian forces would be “the most difficult” to solve.

Ceasefire and territories “are the most difficult moments [of a negotiation]”, he said.

“The first is difficult because it requires courage and political will, the second because it requires a difficult dialogue.”

The Europeans and the US are expected to co-ordinate the application of economic pressure on Putin. National security advisers from Britain, France and Germany were in Washington on Friday for talks with Mike Waltz, their US counterpart.

France and Germany, which have long opposed a full-blown seizure of assets held in the EU, are now warming to the idea and are discussing with the UK and others ways in which they could be used.

Additional reporting by Max Seddon in Berlin and George Parker in London