WASHINGTON (AFP) - President Barack Obama will leave as planned on Saturday for a vacation at Martha's Vineyard, the White House said, just hours after the start of air strikes in northern Iraq.

Mr Obama and his family plan to spend two weeks on the upscale resort island off Massachusetts on the US east coast, where they have taken summer breaks since 2009.

On Sunday August 17, Mr Obama will return for two days to the White House, before heading back out for his holiday, traditionally dedicated to golf, beach picnics, and visits to restaurants.

Asked whether the plan might change given the start of US bombings in Iraq, White House spokesman Josh Earnest said it hadn't been deemed necessary so far.

The president will have with him "an array of communications equipment and national security advisers and others to ensure that he has the capacity to make the kinds of decisions that are required for the commander in chief," Mr Earnest said.

"And if there's a need for the president to return to the White House, it's not a long flight from Martha's Vineyard back to Washington," he added.

Mr Obama announced on Thursday that he had authorized US air strikes to prevent fighters from the so-called Islamic State from attacking the capital of the Iraqi Kurdish region.

The strikes are also designed to break the siege of Mount Sinjar, where IS forces have cornered and reportedly threatened to kill thousands of civilian refugees from the Yazidi religious minority.