WASHINGTON, July 15  -- U.S. President Barack Obama on Tuesday spoke with German Chancellor Angela Merkel by phone, vowing to improve intelligence cooperation between the two countries.

Obama and Merkel exchanged views on U.S.-German intelligence cooperation during their first conversation after a new spy row damaged the allies' relations, and Obama said he would remain in close communication on ways to push cooperation forward, according to a White House statement.

Germany on Thursday asked Washington's intelligence chief in Berlin to leave the country as a new round of allegations of U.S. espionage is threatening to further strained bilateral ties damaged by revelations of U.S. data gathering practices by former U.S. intelligence contractor Edward Snowden last year.

While talking about bilateral relations, the two leaders also discussed the situation in Ukraine and the ongoing talks on Iran's nuclear program, said the statement.

Obama and Merkel reiterated their agreement that Russia must take immediate steps to de-escalate the situation in eastern Ukraine amid the ongoing violence.

They reaffirmed their commitment to working together with other allies to ensure that Europe and the United States remain in close coordination on measures to impose costs on Russia as necessary.

The two leaders said in the call that important gaps remain in the negotiations between world powers and Iran on Tehran's nuclear program, said the statement.

They agreed that Iran must take necessary steps to assure the international community that its nuclear program will be exclusively peaceful.