Merkel's conservatives back ForMin Steinmeier for president - source

German Foreign Minister Frank-Walter Steinmeier waits to address the Parliamentary Assembly of the Council of Europe in Strasbourg, France, October 13, 2016. REUTERS/Vincent Kessler/files

BERLIN (Reuters) - Chancellor Angela Merkel's conservatives agreed on Monday to back Social Democrat Frank-Walter Steinmeier as Germany's next president, creating a vacancy at the foreign ministry at a critical moment in relations with Russia and the United States.

Merkel's camp had hoped to promote its own candidate but chose to back political rival Steinmeier for the largely ceremonial post to avoid a long fight with his party, its partner in the ruling 'grand coalition'.