U.S. President Donald Trump said on Saturday Ukraine should make a deal to end the war with Russia because "Russia is a very big power, and they're not", after hosting a summit where Vladimir Putin was reported to have demanded more Ukrainian land, Reuters reported.

In a subsequent briefing with Ukrainian President Volodymyr Zelenskiy, a source familiar with the discussion cited Trump as saying the Russian leader had offered to freeze most front lines if Kyiv's forces ceded all of Donetsk, the industrial region that is one of Moscow's main targets.

Zelenskiy rejected the demand, the source said. Russia already controls a fifth of Ukraine, including about three-quarters of Donetsk province, which it first entered in 2014.

Trump also said he had agreed with Putin that a peace deal should be sought without the prior ceasefire that Ukraine and its European allies, until now with U.S. support, have demanded, according to Reuters.