WASHINGTON—President Barack Obama and British Prime Minister David Cameron have discussed ongoing national security challenges in Iran, Syria and Afghanistan.

The White House said Obama and Cameron spoke by phone Tuesday. The two leaders discussed their support for talks between world leaders and Iran over its nuclear program, a week of talks in Geneva ended without agreement. Talks are to resume next week.

Obama and Cameron also discussed efforts to strike an agreement between the U.S. and Afghanistan over whether a small U.S. force will remain after 2014. The White House said Obama praised Cameron for supporting talks between Afghanistan and Pakistan in London.

The leaders also discussed progress toward eliminating Syria's chemical weapons and affirmed their support for a proposed international peace conference to end Syria's three-year civil war.