The price of US oil jumped over $2 today, to above $108 a barrel, after the US defence secretary said American forces were ready to act on any order by President Barack Obama to strike Syria.

US benchmark crude for October delivery was up $2.12 to $108.04 a barrel in electronic trading on the New York Mercantile Exchange.

The contract fell 50 cents, or 0.5%, to close at $105.92 last night.

Brent crude was up $1.91 to $112.64 a barrel on the ICE Futures exchange in London.

The price of oil has risen about 15% in the past three months on concern that unrest in Egypt and civil war in Syria could disrupt production and exports, especially from Libya and Iraq. 

It has also raised the spectre of spreading violence that could block important supply routes.

"The political uncertainty across Middle East has dominated the oil market in the last few months, providing upside momentum as the political and economic conditions remain very tentative," analysts said.

The US Secretary of State, John Kerry, appeared to be making a case for an aggressive response to the Syrian conflict when he said there "undeniable" evidence of the Damascus gas attack which killed hundreds of people.