Russia's military backing for the Syrian regime only risks sending more extremists to the war-torn country and could further hamper any effort at bringing peace, US Secretary of State John Kerry said Sunday.

German Foreign Minister Frank-Walter Steinmeier "and I agreed that continued military support for the regime by Russia or any other country risks the possibility of attracting more extremists and entrenching Assad and hinders the way for resolution," he told reporters after a meeting with his German counterpart.