Iraq crisis
A tribal fighter aims his weapon during an intensive security deployment to fight against militants of the Islamic State, formerly known as the Islamic State of Iraq and the Levant (ISIL), in the town of HadithaReuters

Iraqi forces have said they have fortified key positions around the strategic Haditha dam, the second largest in Iraq, with the help of US airstrikes as President Barack Obama is poised to outline a detailed strategy to defeat the Isis militants.

Despite repeated attempts by the Isis jihadists, the Iraqi forces have maintained their hold over the dam.

Security personnel have cleared the area surrounding the dam, which supplies water to millions of people in the western and southern parts of the country.

The US had launched targeted airstrikes around the area at the request of Iraqi forces, said American officials. More than a dozen militants are believed to have been killed in the coordinated attack.

"At the request of the Iraqi government and in keeping with our mission to protect US personnel and facilities, US military planes have begun striking ISIL terrorists near the Haditha dam," an American official was quoted as saying by Al Jazeera.

Iraqi helicopters also took part in the aerial offensive, the country's defence ministry said. The aim of the entire operation, under US cover, was to recapture the region around Barawana, a few kilometres from Haditha.

Though Haditha city and its dam have largely been under the control of Iraqi forces and local tribes, the Isis Sunni extremists have made several attempts to seize it. If the Islamists take over the dam it would be catastrophic as any damage to it could flood the entire province.

"We conducted these strikes to prevent terrorists from further threatening the security of the dam, which remains under control of Iraqi security forces -- with support from Sunni tribes," Pentagon spokesperson Rear Admiral John Kirby told reporters.

Meanwhile, Obama is to announce a detailed strategy to tackle the growing Isis threat.

"I just want the American people to understand the nature of the threat and how we're going to deal with it and to have confidence that we'll be able to deal with it," he told NBC's Meet the Press.

Obama, who will address the nation on the strategy later this week, added: "This is not the equivalent of the Iraq war. This... is similar to the kinds of counterterrorism campaigns that we've been engaging in consistently over the last five, six, seven years.

"I just want the American people to understand the nature of the threat and how we're going to deal with it and to have confidence that we'll be able to deal with it."