WASHINGTON » President Barack Obama’s efforts against the Islamic State should be “sped up and intensified,” and the U.S. needs closer alignment with Turkey and Saudi Arabia to prevail, former Defense Secretary Robert M. Gates said Sunday.

“Those two really do have to be onboard or we have to be onboard with them in terms of priorities,” said Gates, who appeared on NBC’s “Meet the Press.”

Joining closely with Turkey and Saudi Arabia, Gates suggested, would also place the U.S. more squarely against the regime of Syrina President Bashar Assad, who is fighting the Islamic State, or ISIS, and other factions within his country.

Turkey and Saudi Arabia, Gates noted, “are united in the fact that Assad has to go before you can make any real progress against ISIS. I think we need to listen to them if we want them to be active and aggressive members of the coalition.”

Gates’ comments underscore the challenge of defeating ISIS while navigating the region’s other geopolitical undercurrents: The Saudis fear a rising Iran, and Turkey feels threatened by ethnic Kurds. Yet the Kurds and Iran are fighting against ISIS — and Russia has intervened militarily in Syria to bolster Assad.

The attacks launched by ISIS in Paris and against a Russian airliner, said Gates, make clear that Obama must accelerate his efforts.

“We obviously have some strong allies like France,” Gates said, adding the U.S. also needs “to have some allies in the region where we’re on the same page and where we have the same strategy. … We need to understand who is going to be critical to what is happening in Syria, itself.”

Two Republican U.S. senators, Lindsey Graham of South Carolina and John McCain of Arizona, reiterated their call for Obama to deploy thousands of U.S. troops to fight ISIS in Syria and Iraq, in partnership with “regional” allies.

“We will turn to Assad and say, ‘You must go,’ ” said Graham, who appeared with McCain on CBS’ “Face the Nation” from the U.S. Embassy in Baghdad. “Russia and Iran will be on the outside looking in to an entire regional army. … They will fold like a cheap suit.”