The US has armed drones flying over Baghdad to protect US troops that have recently arrived to assess Iraq's deteriorating security, the Pentagon said on Friday.

The military for more than a week has been flying manned and unmanned aircraft over Iraq, averaging a few dozen sorties daily for reconnaissance.

The decision to arm some of the drones follows the deployment to Baghdad of troops who will advise and assist Iraqi counter-terrorism forces.

"The reason that some of those aircraft are armed is primarily for force protection reasons now that we have introduced into the country some military advisers whose objective will be to operate outside the confines of the embassy," the Defence Department's press secretary, Navy Rear Adm. John Kirby, told a Pentagon press conference.

So far, 180 of 300 troops promised by Obama have arrived in the country. They consist of 90 advisers and 90 who are setting up an operations and intelligence analysis unit.

Targeting rebel leaders

Using US air assets to target rebel leaders is one of the options being prepared for President Barack Obama as he considers what support to provide to Iraq, the chairman of the Joint Chiefs of Staff, General Martin Dempsey, said in a radio interview. Protection of critical infrastructure is part of that option, he said.

"We're flying a great deal (of) manned and unmanned ... intelligence and reconnaissance assets, and we're building a picture so that if the decision were made to support the Iraqi security forces as they confront (ISIL), we could do so," Dempsey said.

A handful of Predators armed with Hellfire missiles are being used over the capital for the new force protection mission, a senior defence official said. The official was not authorised to discuss the new flights on the record and requested anonymity.

Officials stressed that Obama still has not authorised airstrikes against rebels who have been claimed territory in other parts of the country.

Source: AP