The United States and its allies will impose "significant and unprecedented" economic measures against Russia if it attacks Ukraine, U.S. Vice President Kamala Harris said on Saturday.

"National borders should not be changed by force," she said at the Munich Security Conference.

"I can say with absolute certainty if Russia further invades Ukraine the United States, together with our allies and partners, will impose significant, and unprecedented economic costs," she said.

"We have prepared economic measures that will be swift, severe, and united," Harris added. "We will target Russia's financial institutions and key industries."

She said Washington would not stop with economic action, but would further reinforce NATO's eastern flank.

Harris added that the United States and its allies remained open to diplomacy but said Russia's "actions simply do not match their words".

She was expected to meet Ukrainian President Volodymr Zelenskiy in Munich later on Saturday in what would be a show of diplomatic support for the European nation, a day after President Joe Biden said he was "convinced" Russia had made a decision to invade Ukraine. [L1N2UU05Z]

Russia, which has said it has no plans to invade, wants to stop Kyiv from joining NATO and accuses the West of hysteria.

On Friday, Harris met NATO Secretary-General Jens Stoltenberg and leaders from three Baltic nations and said Russia must show it is open to diplomacy, while heralding unity in the 30-member NATO alliance and warning Moscow of severe consequences if it invades Ukraine.