The Syrian government is welcoming U.S. help to fight extremist militants within its borders but only if Damascus is warned first and consents to the airstrike plans.

"Everyone is welcome, including Britain and the United States, to take action against ISIS and Nusra with a prior full coordination with the Syrian government," Foreign Minister Walid al-Moallem told reporters Monday.

The Assad regime has been fighting a three-year civil war, and ISIS over the weekend gained serious ground, taking control of a major air base in north-central Syria.

Attacks against ISIS would put the U.S. in the awkward position of strengthening the government of Syrian President Bashar Assad after the Obama administration spent the last three years calling on him to step down.

On Monday, White House spokesman Josh Earnest implied that the Pentagon was preparing military plans for expanding the fight into Syria as a matter of routine, but he declined to say whether that meant Obama was leaning toward that option.

“I’m not going to be in a position to talk about the communications at this point between those military advisers and the advice that they’re offering the commander in chief,” he said.

The comments followed a familiar pattern for the White House, which has tried to raise the possibility of military action in Syria without committing to any particular course of action.

Last week, Chairman of the Joint Chiefs of Staff Martin Dempsey warned that ISIS had an “apocalyptic, end-of-days strategic vision” and could not be defeated without military action in Syria, although he then said he didn’t expect the U.S. to take any.

That may be because of Obama's earlier problems with being too specific. When Assad first began cracking down on domestic dissent in 2012, Obama warned that any use of chemical weapons would cross a "red line" and trigger a U.S. military response.

That caused headaches for Obama when credible evidence emerged in 2013 that the Syrian government had used sarin gas.

Now, as the administration attempts to halt the spread of the militant group ISIS in Iraq, Obama appears to be leaving his options open.

With midterm elections just two months away, Congress is reacting to the possibility of military action along polarized lines.

Sen. Lindsey Graham, R-S.C., on Monday accused Obama of “becoming derelict in his duties” as commander in chief to protect the homeland from terrorist attacks by failing to aggressively confront ISIS wherever they reside, including in Syria.

Meantime, a key Democrat urged caution, noting that U.S. intelligence capabilities in Syria aren't sophisticated enough to separate ISIS from other groups and rebel forces fighting Assad that the U.S. supports.

Rep. Adam Schiff, D-Calif., who serves on the Intelligence Committee, told NBC News that he doubts Obama will support airstrikes in Syria.

“I don’t think that’s going to happen,” he said. “I think he’s going to hear out the military commanders and what their recommendations or options are. But we don’t have the same capabilities on the ground in Syria that we do in Iraq."