The Secretary of Defense, Chuck Hagel, says the US military is ready for any option the president might decide to take against Syria, after last week's poison gas attack in Damascus.
"We have moved assets in place," Hagel told the BBC.
But Hagel added the US and its allies are still trying to confirm the assumption that the Syrian government is responsible for the chemical attack.
The BBC's Defense and Diplomatic correspondent, Jonathan Marcus, says action could start by the end of the week.
Britain and France have said they're willing to support an action, while the Arab League on Tuesday condemned the Syrian government for the chemical attack, calling it a "heinous act."