Washington -- Prime Minister Tony Blair began his last trip here as British leader Wednesday, armed with a parting shot to global opinion that US isolation would make a restive world far more dangerous.

US President George W. Bush greeted his closest foreign ally warmly before the two headed into a private dinner that aides said would be dominated by talks about the US-led "war on terror."

US President George W. Bush (L) walks with British Prime Minister Tony Blair (C) and First Lady Laura Bush (R) as he arrives at the White House in Washington, DC. Blair began his last trip here as British leader Wednesday, armed with a parting shot to global opinion that US isolation would make a restive world far more dangerous.[Agencies]

Blair looked startled by a barrage of flashes from photographers chronicling his last White House meetings with Bush before he steps down on June 27, after a decade in power. "You're a famous person," his host quipped.

The two leaders were due to hold a press conference in the White House Rose Garden at 1525 GMT Thursday, heralding the end to a tumultuous partnership forged in the heat of the September 11 attacks of 2001 and the war in Iraq.

Despite the crippling cost that his support of Bush inflicted on his popularity at home, Blair insists that he did the right thing.

"I believe our country should be a strong ally of America, and I've never had any problem with that," he said in an interview with US network NBC recorded Tuesday.

"I think it will be a very dark day for my country when we do have a problem with it," Blair said.

"The biggest danger is if America disengages, if it decides to pull up the drawbridge and say to the rest of the world, 'Well you go and sort it out.' We need America engaged."

After famously discovering a shared taste for Colgate toothpaste at their first meeting, the Republican president and the British Labour leader marched in lock-step through many of the world's hot-spots over the past six years.

Blair said he had learned to live with taunts of being Bush's "poodle" or "lapdog."

"I've found him immensely straightforward to deal with, someone always true to his word and someone who's a very strong leader," he told NBC.

"Obviously my relationship with President Bush has been of a different order and a different nature, because it's September 11-governed."

The blood-soaked insurgency in Iraq and enduring threat from the Taliban in Afghanistan form part of a "broader global struggle," Blair added.

"And if we back away, if we give up on it, if we show any signs of retreat at all, then the enemy we face worldwide will be strengthened."

Bush paid his own fulsome tribute to Blair last Friday, after the British leader announced his departure and paved the way for the near-certain takeover of 10 Downing Street by his Treasury chief, Gordon Brown.

"I'm going to miss him. He's a remarkable person. And I consider him a good friend," Bush said.

Given their mutual admiration, some observers have anticipated a White House love-in at the Bush-Blair talks.

But according to the White House, there is no shortage of thorny issues to thrash out, from Iraq and Afghanistan to Middle East peace and Iran's nuclear ambitions, via climate change, the Darfur "genocide" and trade liberalization.

In any case, Blair's departure does not signal a greater isolation for Bush or an erosion in British support for his "war on terror," US officials insist.

"I think it's pretty clear, if you take a look at the resolve of the British government, it has been firm," White House spokesman Tony Snow said Tuesday.

Peter Beinart at the Council on Foreign Relations in New York said that "truth be told, Blair's influence was waning because his policy was so unpopular in Britain itself."

"You could argue the other way that Brown, with a fresh mandate and relatively untainted by Iraq, could be a much stronger partner than Blair for Bush if, say, there's a showdown with Iran," he said.