Top leaders at the Pentagon are considering a range of options to bolster the military campaign against the Islamic State in Iraq and Syria (ISIS), including embedding some U.S. troops with Iraqi forces, according to two U.S. officials.

U.S. military commanders have forwarded several options to the Defense Department in the last few weeks, the officials told The Hill, as part of a mounting push within the administration to more aggressively target the terrorist group.

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One of the options presented was embedding U.S. troops with Iraqi security forces; they would have the ability to call in airstrikes, a step that would bring American forces to the front line.

But even without a role in direct combat, that option would skirt close to having “boots on the ground” in Iraq — something President Obama has vowed not to do in the military campaign against ISIS.

The White House has repeatedly said U.S. troops would not have a "combat role" or be engaged in "large-scale ground combat" in Iraq.

A second option sent to Pentagon leaders would embed U.S. forces with Iraqis closer to the battlefield, at the level of a brigade or a battalion.

U.S. troops are now embedded with Iraqis at the division level, which keeps them stationed at headquarters.

Some of the options sent to Pentagon leaders would entail high risk for U.S. troops in Iraq and require more personnel, one of the officials said.

Defense Secretary Ashton Carter and Chairman of the Joint Chiefs of Staff Marine Gen. Joseph Dunford will have an opportunity to discuss the options for the ISIS campaign when they testify Tuesday in front of the Senate Armed Services Committee.

One of the biggest topics of discussion at the hearing will be the way forward in Syria, where the White House recently suspended a program to train and equip rebel forces after it fell woefully short of expectations.

After six months, the program had produced only about 80 rebels, compared with a target number of 5,000 by the end of the year. Some of the trainees admitted to handing over U.S.-supplied equipment to al Qaeda affiliate the Nusra Front.

Complicating the situation in Syria further, Russia has launched an airstrike campaign in the country to shore up President Bashar al-Assad.

Another option under consideration, one of the officials said, is to send more ammunition and weapons to a coalition of rebel groups battling ISIS and Assad's regime. The U.S. military recently airdropped 50 tons of ammunition to the Syrian Arab Coalition, which includes about a dozen Syrian rebel groups.

Also under consideration is increased targeting of ISIS's production and sale of oil on the black market. The U.S.-led military coalition has struck oil refineries controlled by ISIS, but officials are looking at using different kinds of weapons to target the facilities.

Carter on Friday gave some insight into his thinking when he said he expected U.S. troops to conduct more raids in the war against ISIS.

"There's always a look at doing more of what works well and doing less of what doesn't work well, and refining our efforts. That will continue," Pentagon spokesman Navy Capt. Jeff Davis told The Hill on Monday.

"You heard the secretary allude to the one thing Friday, which is the fact that we're going to do more of these enabling missions and advise and assist and enabling missions outside the wire with trusted partners.

"Clearly there's desire to do whatever it takes to degrade and defeat ISIL," he added, using a different acronym for ISIS.

The proposals could face a backlash from liberals on Capitol Hill.

Rep. Jim McGovern (D-Mass.), who opposed the Iraq War in 2002, said the Pentagon’s consideration of embedding U.S. troops with Iraqi forces “extremely concerning”

“We have been repeatedly reassured that the U.S. would not have a combat role in the war against ISIS, but this suggests just the opposite,” he said. “This potential escalation is just the latest evidence that it is long past time for Congress to act. Our brave men and women in uniform are doing their duty.”

“It’s time for members of Congress to do our duty by voting on an Authorization for the Use of Military Force that clearly defines the U.S. military campaign against ISIS before it becomes another endless war," he added.

-- Updated at 6:34 p.m.