WASHINGTON (AFP) - After months vowing to get US troops home from Iraq, Barack Obama has succumbed to the war's political entanglements, struggling to explain his plan in the light of recent security gains.

More than five years after the US invasion, the Iraq war is now enmeshing not only the Bush administration which started it, but both men fighting to inherit it, Democratic White House hopeful Obama and Republican John McCain.

Obama is torn between a vow to end the war, which underpinned his win over Democratic foe Hillary Clinton and Republican claims his plan invites US humiliation, would delight terrorists and waste gains bought in American blood.

The war remains broadly unpopular, but it has fallen behind the economy as the top campaign issue after a lull in violence.

Under rising Republican pressure, Obama last week said he may "refine" his policies after meeting US commanders in Iraq on a trip expected this month.

But hours later, he hurriedly called a second press conference to insist he had not made the "flip flop" on Iraq that many observers are expecting, as he retools his message for the political center ground.

"I have seen no information that contradicts the notion that we can bring our troops out safely at a pace of one to two brigades per month," a frustrated Obama said.

"My first day in office, I will bring the Joint Chiefs of Staff in, and I will give them a new mission, and that is to end this war.

Obama says he can get most US combat troops home within 16 months, leaving behind a smaller force to fight terrorism and protect the US embassy.

He wants to redirect resources to Afghanistan, where more US and coalition troops were killed last month than in Iraq.

On Saturday, the Illinois senator chided the media, saying he had been "puzzled" by the media "frenzy" set off by his comments.

But the episode exposed him to Republican charges he was inexperienced, indecisive, confused on Iraq and ready to ditch past positions to win.

It also highlighted Iraq's lingering capacity to wreak political chaos, the subtle balancing act Obama must pursue.

"The needle that he has to thread is staying on message and linking McCain to Iraq inexorably, while taking half a step backward from the most forceful enunciations of his desire to get out," said analyst Justin Logan, of the Cato Institute.

The McCain campaign relished Obama's struggles, claiming he had finally endorsed his rival's strategy on Iraq.

"He has held almost every conceivable position over the term of his relatively brief career in the senate," McCain foreign policy advisor Randy Scheunemann told reporters on Sunday.

"It has been 910 days since Obama has been to Iraq so it is understandable if he is a little unclear what the situation on the ground is."

Independent Senator Joe Lieberman, a top McCain surrogate, speaking on US television Sunday also pointed out Obama's dilemma.

"For long time, Senator Obama said let's get those troops out as quickly as we can, regardless of what's happening on the ground," said Lieberman on ABC television.

"John McCain had the guts to say in 2003 to the Bush administration ... 'our policy in Iraq is failing. We need more troops,' when everybody else was saying 'pull the troops out'," he said.

"Now his policy is working. Iraq is succeeding. And Senator Obama has to deal with that inconvenient truth."

Meanwhile, Obama partisan Senator Jack Reed, an expert on defense issues, insisted that the Illinois senator's underlying message on Iraq is unchanged.

"Senator Obama is outlining a strategy to redeploy our forces out of Iraq. Senator McCain has a strategy of staying there indefinitely. That is the key, significant strategic difference," Reed said.

While he enjoyed his rival's struggles, McCain, despite being an early critic of Bush war policy, and early advocate of the surge, is still in a dicey spot.

His reluctance to pull US troops out quickly appears at odds with much of American public opinion, and brackets him with the highly unpopular President George W. Bush.

According to the latest CNN/Opinion Research poll, 30 percent of Americans favor, and 68 percent now oppose the war.

Sixty-four percent believe US troop numbers should be cut, compared to 33 percent who think they should remain the same.

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