Keir Starmer vowed Thursday to remain Britain's prime minister despite a storm over his appointment last year of disgraced politician Peter Mandelson, linked to late U.S. sex offender Jeffrey Epstein, as Britain's envoy to Washington.

"I intend to go on doing that vital work for our country because I believe it is the absolute focus and of first importance for this government," he told reporters, after apologizing to the victims of Epstein for believing Mandelson's "lies" about their ties.

Ukraine and Russia have conducted their first prisoner exchange in months, each releasing 157 captured soldiers, Russia's defense ministry said Thursday, amid U.S.-brokered talks in Abu Dhabi aimed at ending the war.

"On February 5, 157 Russian servicemen were returned" from Ukraine, the defence ministry said in a statement. It added that "in exchange, 157 prisoners of war of the Ukrainian Armed Forces were handed over."

President Donald Trump said Wednesday that he and Chinese President Xi Jinping discussed the situation in Iran in a wide-ranging call as the U.S. administration pushes Beijing and others to further isolate Tehran.

Trump said the two leaders also discussed a broad range of other critical issues in the U.S.-China relationship, including trade and Taiwan and his plans to visit Beijing in April.

China said on Thursday it would not join nuclear talks "at this stage" after the expiry of the U.S.-Russian START treaty triggered fears of a global arms race.

"China's nuclear capabilities are of a totally different scale as those of the United States and Russia (and) will not participate in nuclear disarmament negotiations at this stage," Beijing's foreign ministry spokesman Lin Jian told a news conference.

Russia said Thursday there had been "progress" in talks with Ukraine in Abu Dhabi on finding an end to the four-year-war sparked by Moscow's full-scale invasion of its pro-Western neighbor.

"There is definitely progress, things are moving forward in a good, positive direction," Russian negotiator Kirill Dmitriev told state media.

Nuclear talks between Iran and the United States will take place Friday in Oman, the Iranian foreign minister said, as tensions between the countries remain high following Tehran's bloody crackdown on nationwide protests last month.

The announcement Wednesday by Iranian Foreign Minister Abbas Araghchi came after hours of indications that the anticipated talks were faltering over changes in the format and content of the talks. U.S. President Donald Trump, meanwhile, sent a blunt warning to Iran's Supreme Leader Ayatollah Ali Khamenei ahead of the talks.

Russian leader Vladimir Putin hailed Moscow's economic, political and security ties with Beijing as a "stabilizing" factor in turbulent times globally, in a video call with China's Xi Jinping on Wednesday.

Moscow and Beijing have sought to present a united front against the West, with ties deepening since Russia's 2022 Ukraine offensive.

U.S. President Donald Trump on Tuesday called for Americans to move on from the Jeffrey Epstein scandal and again said he had been cleared by the latest release of millions of documents.

"Nothing came out about me other than it was a conspiracy against me, literally, by Epstein and other people. But I think it's time now for the country to maybe get on to something else like health care or something that people care about," he told reporters at the White House.

A second round of peace negotiations between Russia and Ukraine mediated by the United States has begun in the United Arab Emirates, Ukraine's lead negotiator announced Wednesday.

"Another round of negotiations has begun in Abu Dhabi," the head of the Ukrainian delegation, Rustem Umerov, wrote on social media, adding Kyiv's team was seeking "to achieve a just and lasting peace."

The last remaining nuclear arms pact between Russia and the United States is set to expire Thursday, removing any caps on the two largest atomic arsenals for the first time in more than a half-century.

The termination of the New START Treaty would set the stage for what many fear could be an unconstrained nuclear arms race.