LONDON - Prime Minister Tony Blair told U.S. President George W. Bush in 2002 that Britain would back military action if diplomatic efforts to disarm Iraq's Saddam Hussein failed, his former communications chief said on Tuesday.

Appearing before a public inquiry into the Iraq war, Alastair Campbell said there never was a precipitate rush to war despite the close ties between Blair and Bush.

However, Campbell said that Blair wrote personally to Bush to offer his support for military action if Saddam did not accede to United Nations' demands on disarmament before the March 2003 invasion .

If that cannot be done diplomatically and it is to be done militarily, Britain will be there. That would be the tenor of the communication to the president, Campbell told the inquiry. He described the letters as very frank.

Britain sent 45,000 troops to support the U.S.-led invasion despite widespread doubts about its legality and mass protests against it on the streets of London seven years ago.

Many supporters of centre-left Labour remain angry at Blair for leading Britain into a war in which 179 British soldiers were killed.

An official Dutch investigation, whose release was broadcast live on state television, was scathing about the Netherlands' involvement in the war. The Committee of Inquiry on Iraq said The Hague government supported the war without legal backing and did not fully inform parliament about its plans.

Campbell, a former journalist who was one of Blair's closest advisers from 1994 to 2003, said Blair had tried all along to disarm Saddam by diplomatic means.

I think the prime minister was all the way through this trying to get it resolved without a single shot being fired, he said.

He said that Blair, prime minister from 1997 to 2007, was concerned about the links between weapons of mass destruction, rogue states and terrorism and that these fears pre-dated the Sept 11, 2001 attacks on the United States by al Qaeda. No such weapons have ever been found in Iraq.

The five-person inquiry is seeking to learn lessons from the Iraq war. Blair is expected to appear before it in the next few weeks.

The inquiry comes at a sensitive time in British politics, with an election due by June which the opposition Conservatives are forecast to win.

Campbell said that current Prime Minister Gordon Brown, who served as finance minister under Blair, was one of the key circle of advisers to Blair.

Gordon Brown would have been one of the key ministers that he would have spoken to regularly, Campbell said. Brown will not appear before the inquiry until after the election.

Campbell, who is now an informal adviser to Brown, left his job in 2003 after a huge public row with the BBC over claims the government exaggerated intelligence in the run-up to the war.

Campbell defended his actions and said that French and German intelligence services were also concerned about Saddam's weapons despite their subsequent opposition to the war.
Nobody was really saying that Saddam Hussein did not have weapons of mass destruction and that he wasn't a potential threat with them, he said.

(Editing by Ralph Boulton)