Russian support for Assad has 'exacerbated' Syria conflict: US

Russia warned that any move by Gulf nations to send troops to support the rebels in Syria would risk the outbreak of a 'new world war'

The United States has accused Russia of worsening the brutal Syrian conflict with its military action in support of President Bashar al-Assad, as international talks unfolded in Munich on ways to resolve the crisis.

"It has been Russian support for the Assad regime over the past months, and most recently in the siege on Aleppo, that has exacerbated, intensified the conflict," State Department deputy spokesman Mark Toner told reporters yesterday.

Toner's comments came after Russian Prime Minister Dmitry Medvedev warned that any move by Gulf nations to send troops to support the rebels in Syria would risk the outbreak of a "new world war."

The State Department spokesman said that Moscow, with its air strikes that begun on February 1 over northern Syria, had "put the political process in jeopardy" as world powers try to put a stop to a ferocious civil war that has dragged on for nearly five years.

Foreign ministers gathered in Munich struggled to make any headway today on efforts to obtain a ceasefire. US Secretary of State John Kerry was among those present, along with his Russian counterpart Sergei Lavrov.

"It is very concerning," Toner said.

Kerry has "spoken to the fact that given the disparate groups on the ground in Syria, the different factions and the different elements on the ground fighting each other, that this could worsen and could become a broader conflict," he added.

In response to a question about Medvedev's warning, Toner said, "If that is Russia's concern, then they should look at what they're doing to support the Assad regime."

For a week, the United States has been calling for an immediate ceasefire in Syria and humanitarian access to besieged rebel cities but has threatened an unspecified "Plan B" if talks fail.

Moscow has refused to confirm reports that its ceasefire would take effect only on March 1, giving another three weeks to an offensive which the UN says could place 300,000 people under siege.