He added that he did not try to impose a deadline on Moscow

US President Donald Trump has denied claims that Russia rejected his proposal for a Ukraine ceasefire. He reiterated that he remained optimistic about ending the conflict. 

Trump briefly spoke to reporters outside the White House on Friday. He said that he "had a couple of good conversations today" about Ukraine, without elaborating.

A journalist asked Trump whether he had presented a deadline for a ceasefire to Russian President Vladimir Putin. "Not a deadline, but I think we'll have [a ceasefire]... I think we'll have it done fairly soon," Trump said.

Another reporter asked, "Why won't you impose sanctions on Russia after Putin rejected your ceasefire offer?"

Trump replied, "He didn't reject anything, and they do have sanctions. They have a lot of sanctions." 

After his phone call with Trump on Tuesday, Putin ordered the Russian troops to pause strikes on Ukrainian energy infrastructure for 30 days. Although Ukrainian leader Vladimir Zelensky later claimed that Kiev was also respecting the 'energy truce,' Moscow accused Ukraine of violating the arrangement.

"We believe that the truce proposed by the United States has already been violated by Kiev," Foreign Ministry spokeswoman Maria Zakharova said on Thursday. 

Kremlin spokesman Dmitry Peskov told journalists on Friday that Putin's order to halt attacks on energy sites remained active. 

Putin has said that he agreed to Trump's proposal for a 30-day comprehensive ceasefire in principle but stressed that a potential agreement must address "a number of significant points," including control over implementation. He further said that Ukraine must stop mobilization, and that Kiev's Western backers must stop the weapons deliveries.