(Adds details from statement)
WASHINGTON, March 2 (Reuters) - President Barack Obama and the leaders of Britain, Germany and Poland expressed "grave concern" on Sunday over Russia's intrusion into Ukraine, which they called a breach of international law and a threat to international peace and security.
Obama spoke with British Prime Minister David Cameron, German Chancellor Angela Merkel, and Polish President Bronislaw Komorowski in a separate phone calls, the White House said.
"The leaders stressed that dialogue between Ukraine and Russia should start immediately, with international facilitation as appropriate," the White House said in a statement.
The four leaders emphasized their support for Ukraine and its efforts to hold elections in May, the White House said. They promised to work together on a package of financial aid to help the country stabilize its tottering economy. (Reporting by Mark Felsenthal; Editing by Peter Cooney and Meredith Mazzilli)