WASHINGTON (Reuters) - President George W. Bush, winding up eight years in office, expressed regrets on Monday over policies blocked by Congress, weapons of mass destruction not found in Iraq and the harsh political tone in Washington.

But he defended his actions during one of the biggest debacles of his presidency -- Hurricane Katrina of 2005 -- and said history would be his judge after he leaves the White House on January 20.

“You know, presidents can try to avoid hard decisions and therefore avoid controversy. That’s just not my nature,” Bush said in his final press conference before turning power to his Democratic successor Barack Obama.

Bush, by turn wistful, reflective and defiant, conceded that mistakes had been made.

The “Mission Accomplished” banner as the backdrop for a speech on an aircraft carrier in May 2003, less than two months after the invasion of Iraq, was “clearly” a mistake, he said.

“It sent the wrong message. We were trying to say something differently,” Bush said.

The Abu Ghraib scandal of U.S. soldiers mistreating prisoners in Iraq that shocked the world “obviously was a huge disappointment during the presidency,” Bush said.

In recent years an increasingly unpopular Iraq war weighed down Bush’s public approval ratings, which took a further hit from the economic downturn.

The main U.S. justification for the war was that Iraq possessed stockpiles of weapons of mass destruction and posed a threat, but no such weapons were found after the U.S.-led invasion in March 2003.

President George W. Bush is pictured during his last news conference in the Brady press briefing room at the White House in Washington January 12, 2009. REUTERS/Jonathan Ernst

“Not having weapons of mass destruction was a significant disappointment,” Bush said.

KATRINA HITS

He also addressed the heavy criticism for a slow federal response to Hurricane Katrina that struck New Orleans and the Gulf Coast in August 2005.

“I’ve thought long and hard about Katrina,” Bush said. “Could I have done something differently, like land Air Force One either in New Orleans or Baton Rouge?”

But that action would have pulled law enforcement away from helping in the crisis to handle his visit, he said.

Pushing for Social Security reform shortly after re-election in 2004 was a mistake because Congress was unwilling to take on a tough issue that it did not see as an imminent crisis, Bush said. Instead he should have argued for immigration reform, he said.

“I think historians will look back and they’ll be able to have a better look at mistakes after some time has passed,” Bush said. “There is no such thing as short-term history.”

Bush said he had been disappointed by the tone in Washington and had tried to avoid engaging in “needless name-calling.”

Obama will also face harsh critics, “and he’ll be disappointed at times by the tone of the rhetoric. And he’s going to have to do what he thinks is right,” Bush said.

“And if you don’t, then I don’t see how you can live with yourself,” he said. “I don’t see how I can get back home in Texas and look in the mirror and be proud of what I see if I allowed the loud voices, the loud critics, to prevent me from doing what I thought was necessary to protect this country.”