WASHINGTON (AP) — Signaling a possible escalation of U.S. military action in the Middle East, Defense Secretary Ash Carter said Tuesday that the United States is retooling its strategy in Iraq and Syria and would conduct unilateral ground raids if needed to target Islamic State militants.

The U.S. has done special operations raids in Syria and participated in a ground operation to rescue hostages last week in northern Iraq that resulted in the first U.S. combat death in Iraq since 2011. Carter did not say under what circumstances the U.S. might conduct more ground action, but said, "Once we locate them, no target is beyond our reach."

"We won't hold back from supporting capable partners in opportunistic attacks against ISIL, or conducting such missions directly, whether by strikes from the air or direct action on the ground," Carter said, using an acronym for the militant group.

Carter and Marine Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, testified before the Senate Armed Services Committee. Republicans harshly criticized the Obama administration's strategy in Syria and Iraq, where IS militants have captured large swaths of territory and have largely fought the U.S.-led coalition to a stalemate.

With little recent progress in defeating the militant group, the defense secretary's testimony outlined a changing U.S. approach to the fight against IS. The changes point toward the prospect of deeper U.S. military involvement, although President Barack Obama has said he would not authorize a major commitment of ground combat forces.

Among other options being considered is providing close-air support for Iraqi ground forces with Apache helicopters or other aircraft, and embedding U.S. military advisers with smaller Iraqi units, thus placing the Americans closer to the front lines. That's according to defense officials who spoke on condition of anonymity to discuss internal deliberations.

The U.S. now has about 3,300 troops in Iraq to train and advise Iraqi forces and to protect U.S. facilities. There are no U.S. troops in Syria.

Among options being considered is using U.S. Army Apache helicopters and perhaps other aircraft to provide close-air support for Iraqi ground troops in certain circumstances, one U.S. defense official said after Carter testified. The official was not authorized to discuss internal deliberations publicly and thus spoke on condition of anonymity.

The administration also is considering other moves that would place U.S. troops closer to the front lines.

The changes Carter cited focus largely on targeting Raqqa, the militants' declared capital in Syria, and recapturing Ramadi, the capital of Anbar province in western Iraq, which IS fighters captured in May and have successfully defended so far.

In Syria, Carter said the U.S. will support moderate Syrian forces fighting IS militants, who have made territorial gains near Raqqa. He said the U.S. hopes to better equip anti-IS forces, further bolster Jordan and intensify the American air campaign with additional U.S. and coalition aircraft to target IS with heavier airstrikes.

"In the new train-and-equip effort that we described today, we will look to identify and then support capable and motivated forces on Syrian territory that are willing to take on IS," Carter said. "We have identified some of them already. And the new approach is to enable them, train them and equip them, rather than trying to create such forces anew, which was the previous approach."

A Defense Department program to train and equip moderate rebels to combat the Islamic State was a failure, and CIA-backed rebels fighting Assad are now under attack by Russian bombers.

In Iraq, Carter said the U.S. is willing to provide more firepower and other support if the Iraqi government can create a motivated Iraqi force that includes ethnic Sunnis.

"We've given the Iraqi government two battalions worth of equipment for mobilizing Sunni tribal forces. ... If local Sunni forces aren't sufficiently equipped, regularly paid and empowered as co-equal members of the Iraqi security forces, ISIL's defeats in Anbar will only be temporary," Carter said.

If done simultaneously, all the actions in the new U.S. strategy on the ground and in the air "should help shrink IS territory into a smaller and smaller area and create new opportunities for targeting IS — ultimately denying this evil movement any safe haven," Carter said.

Carter testified just weeks after Russia began conducting hundreds of airstrikes in Syria. Moscow says it is trying to help the Syrian government of President Bashar Assad defeat IS, but many of the Russia airstrikes have targeted Syrian rebels in areas where the extremist group is not present.

Carter reiterated his complaint that the Russian approach is "wrong-headed" and suggested a "doubling down on their long-standing relationship with Assad."

"It appears the vast majority of their (the Russians') strikes, by some estimates as high as 85 percent to 90 percent, use dumb bombs, which obviously increases the possibility of civilian casualties," he said.

Carter's testimony drew criticism from Republicans on the committee, primarily because it does not involve the ouster of Assad.

Sen. Lindsey Graham, R-S.C., a presidential candidate, said Russia, Iran and the Hezbollah militant group all are supporting Assad. Carter and Dunford both acknowledged that the U.S. was supporting moderate forces in Syria in the fight against the Islamic State, but not those fighting against Assad.

Carter said the U.S. approach to removing Assad has been mostly a political effort.

Dunford said, "I think the balance of forces right now are in Assad's advantage."

Graham seized on their replies.

"If I'm Assad, this is a good day for me because the American government has just said, without saying it, that they are not going to fight to replace me," Graham said.

"You have turned Syria over to Russia and Iran. ... This is a sad day for America and the region will pay hell for this," Graham said, adding that he thought the U.S. strategy was half-baked. "The Arabs are not going to accept this. The people of Syria are not going to accept this."