US President Obama with former Secretary of State Powell in the Oval Office at the White House in Washington (Reuters)

Former US Secretary of State Colin Powell has endorsed US President Barack Obama in the run for the White House against Republican candidate Mitt Romney, whose foreign policy Powell described as a "moving target".

Powell made his electoral choice public in an interview with CBS This Morning, in which he attacked Romney on several issues.

"Not only I am not comfortable with what governor Romney is proposing for his economic plan, I have concerns about his views in foreign policy" Powell said, before adding: "It's hard to fix it [Romney's foreign policy]; it's a moving target."

Powell also accused Romney of backtracking on his plan for Afghanistan and Iraq, telling CBS viewers that "the governor who was speaking on Monday night at the debate was saying things that were quite different from what he said earlier; so I am not quite sure which governor Romney we will be getting.

"Sometimes I don't sense that he has thought through these issues as thoroughly as he should have."

Powell's attack on Romney was not limited to foreign policy. The retired general added that he is "more comfortable" with President Obama's stance on education, immigration and climate change than that of his opponent, adding that "there are some very, very strong neo-conservative views that are presented by [Romney] that I have some trouble with."

Moving on to healthcare, Powell said: "I do not want to see the new Obamacare plan thrown off the table. It has issues - you have to fix some things in that plan - but what I see is that 30 million of our fellow citizens will now be covered by insurance and I think that is good. We are one of the few nations in the world with our size of population and wealth that doesn't have universal healthcare."

Powell said he voted for Obama also in 2008 and he plans "to stick with him in 2012."

"I think we ought to keep on the track that we are on," he said adding that he still consider himself a Republican but "of a more moderate mold. That's something of a dying breed, I'm sorry to say."