WASHINGTON — The United States is flying F-18 attack aircraft launched from the carrier USS George H.W. Bush on missions over Iraq to conduct surveillance of insurgents who have seized part of the country, a U.S. official said on Thursday.

The official, speaking on condition of anonymity, said the F-18s were being flown from the carrier, which was ordered into the Gulf several days ago, because it is sovereign U.S. territory and can deploy tanker refueling planes if needed.

General Martin Dempsey, the Chairman of the Joint Chiefs of Staff, told lawmakers on Wednesday the United States has been carrying out manned and unmanned intelligence, surveillance and reconnaissance missions over Iraq and was devoting a number of planes and Navy ships to the effort.

U.S. officials have said that President Barack Obama is considering manned or unmanned air strikes as one option for countering gains by insurgents from the Islamic State of Iraq and the Levant. But they say Washington lacks the kind of precise intelligence it needs to conduct strikes effectively.