WASHINGTON – U.S. combat troops may be deployed against the Islamic State of Iraq and Syria (ISIS) if the strategy announced by President Barack Obama last week fails to make substantial progress against the radical Sunni group, Washington’s top military officer warned here Tuesday.

The statement by the chairman of the Joint Chiefs of Staff, Gen. Martin Dempsey, delivered during testimony before a key Congressional committee, suggested for the first time that the administration may substantially broaden military operations in Iraq beyond air strikes and advising Iraqi and Kurdish forces far from the front lines.

“If we reach the point where I believe our advisers should accompany Iraqi troops on attacks against specific targets, I will recommend that to the president,” Dempsey told members of the Senate Armed Services Committee.

“At this point, his [Obama’s] stated policy is we will not have U.S. ground forces in direct combat,” he said. “But he has told me as well to come back to him on a case-by-case basis.”

Dempsey’s remarks, which came as Congress appeared poised to approve a pending 500-million-dollar request to train and equip Syrian rebels committed to fighting ISIS, as well as the government of President Bashar al-Assad, appeared certain to fuel doubts about Obama’s plans, particularly given his promise last week that U.S. forces “will not have a combat mission.”

“We will not get dragged into another ground war in Iraq,” he declared in last week’s nationally televised speech in which he also pledged to build an international coalition, including NATO and key regional and Sunni-led Arab states, to fight ISIS forces in both Iraq and Syria.

While Secretary of State John Kerry has since gathered public endorsements for the administration’s strategy to “degrade and ultimately destroy” ISIS, notably at a meeting of Arab states in Jeddah, Saudi Arabia, last week and from a larger group of nations in Paris Sunday, scepticism over the strength and effectiveness of such a coalition appears to have deepened.

Although Saudi Arabia, the United Arab Emirates (UAE) and France appear committed to provide some air support to anti-ISIS operations, several key allies, including Britain, have remained non-committal about their willingness to help with military operations.

Turkey, whose army is the largest and most potent in the region and whose porous borders with ISIS-controlled regions in eastern Syria have been fully exploited by the group, has been particularly disappointing to officials here.

Despite repeated appeals, for example, Ankara has reportedly refused to permit U.S. military aircraft to use its strategically located Incirlik air base for carrying out anything but humanitarian missions in or over Iraq, insisting that any direct involvement in the campaign against ISIS would jeopardise the lives of dozens of Turkish diplomats seized by the group at Ankara’s consulate in Aleppo earlier this year.

Critics of Washington’s strategy are also concerned that Kerry may have reduced the chances for co-operation with another potentially key anti-ISIS ally – Iran – which he explicitly excluded from participation in any international coalition due to its support for Assad and its alleged status as a “state sponsor of terror”.

While Kerry Monday said Washington remained open to “communicating” with Tehran — which, along among the regional powers, has provided arms and advisers to both Kurdish and Iraqi forces — about its efforts against ISIS, Iran’s Supreme Leader, Ayatollah Ali Khamenei, who earlier this month reportedly authorised limited co-operation over ISIS, ridiculed the notion, insisting that it was Iran who had rebuffed Washington.

But Kerry’s exclusion of Iran from the anti-ISIS coalition, according to experts here, was motivated primarily by threats by Saudi Arabia and the UAE to drop out if Tehran were included – a reflection not only of the ongoing Sunni-Shi’a conflict in the region, especially in the Syrian civil war, but also of the difficulty Washington faces in persuading governments with widely differing interests to unite behind a common cause.