Bucharest -

United States Vice-President Joe Biden says Russia must be punished if it seeks to derail Ukraine's presidential elections this weekend.

“If Russia undermines these elections... we must remain resolute and impose greater costs to Russia and (be) equally resolute to invest in the Nato alliance,” Biden said on Wednesday after talks with Romanian President Traian Basescu.

Speaking during a tour of Eastern European nations, he urged European allies to use their influence and “promote a stable and positive environment” so Ukrainians can vote unhindered on Sunday.

The US and the EU have imposed travel bans and asset freezes on President Vladimir Putin's inner circle over Russia's annexation of Crimea and have threatened to target entire sectors of the Russian economy if Russia tries to grab more land. - Sapa-AP