(Adds additional comment from Dempsey)
By Missy Ryan and David Alexander
WASHINGTON, July 3 (Reuters) - Iraqi security forces will probably not be able to recapture ground they have lost to Islamist militants without assistance, the top U.S. military officer said on Thursday.
General Martin Dempsey, chairman of the U.S. Joint Chiefs of Staff, said U.S. advisers now conducting an assessment of Iraqi forces were reporting the military was "capable of defending Baghdad" but it "would be challenged to go on the offense, mostly logistically challenged."
"If you're asking me will the Iraqis at some point be able to go back on the offensive, to recapture the part of Iraq that they've lost, I think that's a really broad campaign quality question," Dempsey told reporters at the Pentagon. "Probably not by themselves."
Iraq is grappling with an onslaught of Sunni Muslim militants from the Islamic State or ISIL, an al Qaeda offshoot, who have seized large areas of northern and western Iraq and are threatening to march on the capital Baghdad.
Militants were able to seize so much territory in part because forces under Shi'ite Prime Minister Nuri al-Maliki deserted their positions in the face of the militant advance last month.
The United States, which focused much of its effort following its 2003 invasion of Iraq building up Iraq's security forces, is now seeking to help the Iraqi military repel those militants.
At the same time the Obama administration does not want to get bogged down in another war in Iraq, especially with political bickering continuing in Baghdad as officials try to form a new government following an April election.
Both Dempsey and Defense Secretary Chuck Hagel urged Iraqi leaders to form a unity government.
"Unless the Iraqi government gets the message out that it really does intend to allow participation by all groups, everything we're talking about makes no difference," Dempsey said.
Hagel said U.S. forces had established a second U.S.-Iraq Joint Operations Center in Iraq. The new center, in Arbil, the capital of the semi-autonomous northern region, will complement work done by the first center in Baghdad.
U.S. forces also have six assessment teams on the ground in Iraq, Hagel said. The U.S. military presence aims to evaluate the current state of the Iraqi military and how U.S. forces can best act to help the government repel ISIL militants.
While President Barack Obama has said U.S. troops will not return to combat in Iraq, U.S. officials have said the United States might conduct air strikes on ISIL targets if the situation warrants. Dempsey also appeared to open the door to more direct action by U.S. soldiers now in Iraq against ISIL.
"If the assessment comes back and reveals that it would be beneficial to this effort and to our national security interests to put (U.S.) advisers (now in Iraq) in a different role, I will first consult with the secretary. We will consult with the president. We'll provide that option and we'll move ahead," he said. (Reporting By Missy Ryan and David Alexander; editing by Andrew Hay)