By Justin Sink - 03/05/14 05:34 PM EST
President Obama and British Prime Minister David Cameron spoke by phone on Wednesday, expressing "grave concern" over the unrest in Ukraine, according to the White House.
"The leaders expressed their grave concern over Russia’s clear violation of Ukrainian sovereignty and territorial integrity, and both noted that the current circumstances are unacceptable," the White House said in a statement. "Russia has already started to pay a cost for its actions, such as reducing investor confidence in Russia."
British banks and investment firms attract substantial investments from Russia, and many wealthy Russian oligarchs have homes and property investments in London. Earlier this week, a document that appeared to indicate that Downing Street opposed trade sanctions surfaced in the British press.
On Tuesday, British foreign secretary William Hague insisted "all options remain on the table on the diplomatic and economic side," while calling the security breach "regrettable," according to Agence France-Presse.
"Anything that is written in one document being carried by one official is not necessarily any guide to the decisions that will be made by Her Majesty's government," Hague said.
"Our options remain very much open on this subject."
Separately, Obama and Cameron said they welcomed a military observer mission being undertaken by the Organization for Security and Cooperation in Europe at the request of Ukraine.
The team is expected to undertake a monitoring effort of military activity in the Crimea region, in a bid to de-escalate tensions.
The call was Obama's second with a major European ally in less than 24 hours. On Tuesday, he spoke with German Chancellor Angela Merkel for an hour about developments in the former Soviet republic.
According to the White House, the pair discussed ways to calm the crisis, sparked by Russia’s move over the weekend into the Crimean Peninsula, an ethnically Russian region just across the border.
A senior administration official told CNN that Merkel was looking for a way to construct a so-called “off ramp” that would enable Russian President Vladimir Putin to navigate out of the rapidly developing crisis.
Under the proposal, the international community would deploy observers to ensure the rights of ethnic Russians in Ukraine. Putin has suggested those Russian nationals are under threat from the new Ukrainian government, a charge leaders there and in the U.S. have denied.
Vice President Biden, meanwhile, spoke Wednesday afternoon with Latvian President Andris Berzins. The pair "expressed their grave concern over Russia’s clear violation of Ukrainian sovereignty and territorial integrity, and discussed how best to bring about a peaceful resolution," according to the White House.
— This post updated at 6:15 p.m.