Republican presidential candidate Chris Christie met with Ukrainian President Volodymyr Zelenskiy in Kyiv on Friday and underscored strong U.S. support for its fight against Russia.

Christie, once an ally of former President Donald Trump, is challenging him for their party's nomination in the 2024 election - and drawing a stark contrast on Ukraine with front-runner Trump.

Trump's former vice president Mike Pence in June became the first Republican candidate to meet Zelenskiy during the campaign.

Christie visited Ukraine a day after Trump returned to Washington to plead not guilty to federal charges he orchestrated a plot to try to overturn his 2020 election loss to Democrat Joe Biden.

Former New Jersey governor Christie met with Zelenskiy at the presidential palace after visiting a mass grave in Bucha, a town where Ukraine accuses Russian troops of having committed atrocities soon after their February 2022 invasion. He also saw damage in Irpin near Kyiv. Both places were retaken by Ukrainian forces.

Christie said he came to Ukraine to give Americans a view of the war and its toll and he emphasized that he wanted U.S. support to continue. The United States has provided billions of dollars worth of weapons to Ukraine to defend itself.

"I am an advocate for there being more aid to Ukraine, more significant aid to Ukraine, broader aid for Ukraine," Christie told Zelenskiy.

"It's really important to hear all these words from you," Zelenskiy replied.

Christie's stance sets him apart from some of the other Republican candidates including Trump.

Florida Governor Ron DeSantis, a distant second in public opinion polls, this year suggested that the war was simply a "territorial dispute" before backtracking.

Trump, who left office in 2021 after one four-year term, was impeached in 2019 on allegations he pressured Ukraine to investigate Biden. Senate Republicans acquitted him of those charges.