WASHINGTON (Reuters) - Democratic presidential candidate Barack Obama said on Tuesday a “single-minded” focus on Iraq was distracting the United States from other threats and he renewed his vow to end the war.

Democratic presidential candidate Senator Barack Obama (D-IL) addresses supporters during a campaign stop at the NAACP National Convention in Cincinnati, Ohio, July 14, 2008. REUTERS/John Sommers II

“This war diminishes our security, our standing in the world, our military, our economy, and the resources that we need to confront the challenges of the 21st century,” Obama said in excerpts of a speech to be delivered later on Tuesday.

“By any measure, our single-minded and open-ended focus on Iraq is not a sound strategy for keeping America safe,” he said.

Obama, who has been accused by his Republican rival John McCain of shifting positions on Iraq, is seeking to lay out his views on the war ahead of a planned trip to Afghanistan and Iraq soon.

Dates of the trip have not been disclosed for security reasons.

The Democratic candidate’s critics have suggested he was wavering on the 16-month timetable he laid out for the withdrawal of U.S. troops because of his recent comment that he might “refine” his policies on Iraq based on consultations with military commanders.

But Obama has emphasized that while he is open to tactical adjustments, the 16-month timetable for withdrawal remains his goal.

“This war distracts us from every threat that we face and so many opportunities we could seize,” the speech excerpts said. “Instead of being distracted from the most pressing threats that we face, I want to overcome them.”

The future of Iraq promises to be a central issue in the November election battle for the White House between McCain, an Arizona senator, and Obama, an Illinois senator.

SECOND TRIP TO IRAQ

McCain criticized Obama for delivering a speech on Iraq before traveling there.

Obama’s visit to Iraq, where he has only been once, in 2006, and Afghanistan follows repeated criticism from McCain that he should visit the area and talk to commanders.

“Sen. Obama is departing soon on a trip abroad that will include a fact-finding mission to Iraq and Afghanistan,” McCain said in written excerpts of comments he will deliver later on Tuesday in New Mexico.

“And I note that he is speaking today about his plans for Iraq and Afghanistan before he has even left,” McCain said.

“In my experience, fact-finding missions usually work best the other way around: first you assess the facts on the ground, then you present a new strategy,” he added.

A Washington Post/ABC News poll released on Monday found Americans evenly divided on the candidates’ positions on Iraq with 47 percent of those polled saying they trust McCain more to handle the war, and 45 percent having more faith in Obama.

The poll showed the public is also evenly divided on whether Obama could serve effectively as commander in chief with 48 percent saying he would be an effective leader of the military and 48 percent saying he would not.

Obama has highlighted the resurgence of the Taliban in Afghanistan as a threat that has been harder for the United States to tackle because of the distraction of the Iraq war.

He has proposed adding two U.S. combat brigades, about 9,000 troops, to the 36,000 troops already in Afghanistan and said this would be made possible by a drawdown of troops from Iraq.

“I have argued for years that we lack the resources to finish the job because of our commitment to Iraq,” Obama said in the speech. “As president, I will make the fight against al Qaeda and the Taliban the top priority that it should be.”

He also called for changes to U.S. policy toward Pakistan, saying that President George W. Bush had offered a “blank check” to Pakistani President Pervez Musharraf in the form of U.S. military aid.

Many Taliban and al Qaeda militants are believed to be hiding in Pakistan along the rugged border area near Afghanistan.

Obama called for tripling non-military aid to Pakistan and said he would co-sponsor a bill to do so.

(Reporting by Caren Bohan; Editing by Eric Beech)