Washington, Apr 19 (IANS/RIA Novosti): Russia fears not only losing its "last bastion" of influence in the Middle East but also what would follow Syrian President Bashal al-Assad, US director of national intelligence James Clapper has said.

Clapper said it Thursday while explaning why Russia refused to join western calls for Syrian President Bashar al-Assad to step down.

Syria "represents their last bastion, I guess, in the Middle East where they have influence. It's been a huge weapons' client of theirs," Clapper told a Senate Armed Services Committee hearing on current and future threats to the US.

"I also think they are concerned about what would happen after Assad in the be-careful-what-you-ask-for department," he said.

Washington believed that Syria would be controlled by factions "when Assad falls", adding that was "a question of time", he said.

Russia has vetoed two UN resolutions imposing sanctions on Assad's regime.

On Wednesday, Russia said the Friends of Syria group was playing a 'negative role' in the Syrian conflict by encouraging extremists to seize power in the country.

The Syrian conflict, which started in March 2011 with peaceful protests demanding reforms, has gradually turned into a civil war in response to the government's military crackdown on the protesters.

More than 70,000 people have been killed in the conflict, and nearly 1.4 million are registered as refugees in neighboring countries, according to the UN.

Some 400,000 Syrians have fled the country in the last seven weeks alone, UN High Commissioner for Refugees Antonio Guterres said Thursday.

Guterres also warned the security council that almost half of Syria's population of 20.8 million could be in need of humanitarian aid by the end of 2013 unless the conflict ends soon.