-Mitch McConnell, the top Republican in the U.S. Senate, paid an unannounced visit to Kyiv on Saturday with other Republican senators and met Ukrainian President Volodymyr Zelenskiy for talks.
McConnell is pressing Republican Senator Rand Paul to end his opposition to a $40 billion aid package for Ukraine, which has overwhelming support from both major parties.
Zelenskiy hailed what he said was a powerful signal of bipartisan support for Ukraine and the strength of relations between the two nations.
"We discussed many areas of support for our state, including in defence and finance, as well as strengthening sanctions against Russia," he said in a video address, adding he stressed the need for Russia to be designated a terrorist state.
Moscow's ambassador to the United States warned against closer cooperation with Ukraine, saying situation in the region was "extremely dangerous", Tass news agency reported.
"The United States is getting dragged ever deeper into a conflict with the most unpredictable consequences for
relations between the two nuclear powers," Tass quoted Anatoly Antonov as telling Russian television on Saturday.
McConnell was accompanied by fellow Senators Susan Collins, John Barrasso and John Cornyn.
Dozens of foreign politicians and celebrities have visited Ukraine since the Russian invasion in February to show their support. President Joe Biden's wife, college professor Jill Biden, made an unannounced trip to Kyiv last Sunday.