LONDON, March. 2 -- British Prime Minister David Cameron and American President Barack Obama on Sunday "agreed on the urgent need for de-escalation and for Russia to engage in a dialogue directly with Ukraine" in a phone call, a Downing Street spokesperson said in a statement.

"They agreed that Russia's actions were completely unacceptable," the spokesperson said, adding that the two leaders spoke over phone at 9:00 p.m. Sunday.

"They agreed there must be 'significant costs' to Russia if it did not change course on Ukraine," the spokesperson continued.

Cameron and British Foreign Secretary William Hague have decided that "it would be inappropriate for British ministers to attend the Sochi Paralympics in current circumstances," according to an earlier Downing Street statement Sunday.

Also on Sunday, Hague said that Britain will not take part in any of the G8 preparatory meetings in Russia planned for this week.

"The United Kingdom will join other G8 countries this week in suspending our co-operation under the G8, which Russia chairs this year, including the preparation meetings this week for the preparation of the G8 summit," Hague announced the decision prior to his visit to Kiev for talks with Ukraine's new leaders.

Russian President Vladimir Putin said on Saturday that no decision had been made on sending troops to Ukraine, despite the Russian parliament's approval.

European foreign ministers will meet on Monday to discuss the recent developments in Kiev.