"All bases are covered" in a US-led multinational coalition against the Islamic State, John Kerry said, as Washington rallies diplomatic and public support to smash the jihadists.

The US Secretary of State told CBS's Face the Nation that there were allies willing to join the United States in air strikes on IS, which has overrun large swaths of northern Iraq and Syria in a brutal and lightning campaign that has seen beheadings and forced religious conversions.

"Some" had offered to put troops on the ground to defeat IS, Kerry said in the interview aired Sunday, adding: "But we are not looking for that at this moment anyway."

Kerry was speaking in Cairo on Saturday, before news of the latest IS beheading of a Western hostage, Briton David Haines, and ahead of a likely Congress vote this week on President Barack Obama's plan to train and equip Syrian rebels, a key plank in his strategy to destroy IS.

That strategy was outlined Wednesday by Obama in a primetime televised speech to the nation, in which he announced expanded US air strikes in Iraq against IS and said he envisaged new action against the radical group in neighboring Syria.

Obama plans to train "moderate" Syrian rebels to take on IS and to reconstitute the Iraqi army, parts of which fled an IS blitzkrieg across northern and western Iraq.

Kerry, who has been touring the Middle East drumming up support for the US-led coalition, told CBS that allies in the Middle East and beyond were ready to help in the battle against IS, which has executed two American reporters in graphic videos which sparked revulsion.

"Every single aspect of the president's (Obama) strategy, and what is needed to be done in order to accomplish our goal, has been offered by one country or multiple countries, and all bases are covered," Kerry told CBS.

Opposition forces would do the fighting on the ground in Syria, augmented by US and allied air support, he said, adding that Washington would not coordinate air attacks on the militants with the Syrian regime of Bashar al-Assad, but would ensure their forces do not come into conflict.

"We will certainly want to deconflict and make certain that they're (Syria) not about to do something that they might regret even more seriously," Kerry said.

"But we're not going to coordinate, it's not a cooperative effort."

Australia was among the latest to make a concrete commitment to the growing coalition, Prime Minister Tony Abbott saying that Canberra would deploy 600 troops to the United Arab Emirates, a regional Washington ally.

Ten Arab states, including Saudi Arabia, are among the countries backing the coalition.

Speaking in Paris, Kerry's latest port of call on his whistlestop coalition-building trip, a US official said the number of countries signing on was "going up almost every hour," from Europe and the Middle East right across to Japan, South Korea and New Zealand.

- What is success? -

Obama's intent to "degrade and ultimately destroy" IS drew a skeptical response in Washington, with critics noting that even Al-Qaeda has not been eradicated, despite a 13-year US-led war against it.

War-weary Democrats worry that maximalist US goals could suck the United States back into intractable Middle East ground wars, while Republicans criticized the president for not going far enough, having consistently ruled out US troops on the ground.

In a series of interviews on US television Sunday, including on NBC's Meet the Press, White House chief of staff Denis McDonough clarified Washington's goals.

"Success looks like an ISIL that no longer threatens our friends in the region, no longer threatens the United States," he said, using an alternative acronym for the Islamic State, which has declared a "caliphate" straddling Syria and Iraq.

"An ISIL that can't accumulate followers, or threaten Muslims in Syria, Iran, Iraq, or otherwise. And that's exactly what success looks like."

Polls show US public sentiment swinging sharply behind US action since IS posted a video showing the beheading of American hostage James Foley last month. But they also show the public still appears doubtful that the president's strategy will work.