The United States is preparing military options to pressure the Islamic State in Syria, the US military said on Monday, but officials cautioned that no decision had been made to expand US action beyond the limited air strikes underway in Iraq.

President Barack Obama has so far sought a limited military campaign in Iraq focused on protecting American diplomats and civilians under direct threat. Still, officials have not ruled out escalating military action against the Islamic State, which has increased its overt threats against the United States.

General Martin Dempsey, chairman of the Joint Chiefs of Staff, said last week that the Islamic State would need to eventually be addressed on "both sides of what is essentially at this point a non-existent border" between Syria and Iraq.

Dempsey's spokesman confirmed on Monday that options against Islamic State were under review and stressed the need to form "a coalition of capable regional and European partners."

"With Central Command, (Dempsey) is preparing options to address ISIS both in Iraq and Syria with a variety of military tools including airstrikes," Colonel Ed Thomas said.

"The bottom line is that our forces are well postured to partner with regional allies against ISIS."

Please LIKE our Facebook page - it makes us stronger