* Anbar governor concerned about Islamic State seizing dam
* First goal is U.S. air support
* Concerns over militants' opponents stamina for fight
* IS fighters appear to be broadening front against peshmerga (Adds comment from U.S. State Department)
By Raheem Salman
BAGHDAD, Aug 14 (Reuters) - The governor of Iraq's Anbar province in the Sunni heartland said he has asked for and secured U.S. support in the battle against Islamic State militants because opponents of the group may not have the stamina for a long fight.
Ahmed Khalaf al-Dulaimi told Reuters that his request, made during meetings with U.S. diplomats and a senior military officer, included air support for battling the militants who have a tight grip on large parts of Anbar and the north.
Dulaimi said the Americans had promised to help.
"Our first goal is the air support. Their technology capability will offer a lot of intelligence information and monitoring of the desert and many things which we are in need of," he said in a telephone interview.
"No date was decided but it will be very soon and there will be a presence for the Americans in the western area," he said.
Asked whether Dulaimi was correct in saying the United States had made a commitment, U.S. State Department spokeswoman Marie Harf said she had no details but that American officials had met with a range of people in Iraq to discuss their security needs.
"We're having conversations about what it (any security assistance) might look like in the future, but nothing concrete beyond that," Harf told reporters in Washington.
A dramatic push by the Islamic State through northern Iraq to the border with the semi-autonomous Kurdish region alarmed Baghdad and drew the first U.S. air strikes on Iraq since the withdrawal of American troops in 2011.
U.S. involvement in Anbar is a far more sensitive matter.
The region was deeply anti-American during the U.S. occupation, with everyone from ordinary Iraqis to powerful Sunni tribes to al Qaeda taking up arms against U.S. troops.
The United States mounted its biggest offensive of the occupation against a staggering variety of Islamist militants in the city of Falluja in Anbar, with its soldiers experiencing some of the fiercest combat since the Vietnam War.
Eventually, the U.S. military was able to persuade some of its most die-hard Sunni opponents to turn against al Qaeda, which is seen as less hardline than the Islamic State.
The strategy worked for some time, but the sectarian agenda of outgoing Shi'ite Prime Minister Nuri al-Maliki alienated many Sunnis and the Islamic State capitalised on sectarian tensions to gain control of hardcore Sunni cities like Falluja and Ramadi.
"THEY GAVE A PR0MISE"
Iraq's president has named a new prime minister, Haider al-Abadi, who is seen as a moderate Shi'ite with a decent chance of improving ties with Sunnis, who dominated the country during Saddam Hussein's decades of iron-fisted rule.
Dulaimi seemed especially concerned by the militants' determination to seize control of Anbar's Haditha dam - they recently seized Iraq's biggest dam, a fifth oilfield, more towns and areas that are home to vital wheat crops in the north.
"The situation in Haditha, where the dam is, is controlled by security forces and tribes," Dulaimi said. "But the problem is how long can they endure the pressure?"
"I held several meetings since one month ago with the American Embassy and the commander of the central troops all in this regard, and very soon there will be a joint coordination centre and operations in Anbar. They gave a promise," he said.
Aside from strong momentum built up in the north and control of large parts of the west, the Islamic State has threatened to march on Baghdad.
The group, which wants to redraw the map of the Middle East, has been using tunnels built in the 1990s by Saddam to move its fighters, weapons, ammunition and supplies to towns just south of Baghdad, Iraqi intelligence officials told Reuters.
Rough terrain has enabled the militants to evade the army and security forces.
On Thursday, Islamic State militants massed near the Iraqi town of Qara Tappa, 122 km (73 miles) north of Baghdad, security sources and a local official said, in an apparent bid to broaden their front with Kurdish peshmerga fighters.
The movement around Qara Tappa suggests they are getting more confident and looking to grab more territory closer to the capital after stalling in that region.
"The Islamic State is massing its militants near Qara Tappa," one of the security sources said. "It seems they are going to broaden their front with the Kurdish fighters." (Additional reporting by Arshad Mohammed in Washington, writing by Michael Georgy; editing by Peter Millership and Gunna Dickson)