Manuel Balce Ceneta, Associated Press
British Prime Minister Gordon Brown, left, and President Bush participate in a news conference in the Rose Garden.

WASHINGTON — President Bush and British Prime Minister Gordon Brown tried to dispel doubts about their relationship Thursday, showcasing personal bonhomie as well as common ground on vexing issues such as the Iraq war, a showdown with Iran, global trade and the crises in Sudan and Zimbabwe.

Brown, particularly, appeared to make an effort to move beyond the leaders' frosty first meeting in July.

The prime minister, then only a month in office as successor to top Bush ally Tony Blair, was given a coveted invitation to the presidential retreat at Camp David. But he displayed stiff formality that raised questions about whether he would work as closely as Blair had — or much at all — with Bush.

That didn't seem in doubt in the Rose Garden after Thursday's nearly 90-minute Oval Office meeting.

On Iran, Brown offered staunch support for his host's tough stance on the need to rein in Tehran's nuclear program.

Brown said "I make no apology" for seeking to persuade European leaders to extend European sanctions against Iran, to include investments and liquefied natural gas. "Iran is in breach of a nonproliferation treaty," he said. "Iran has not told the truth to the international community about what its plans are."

On Iraq, Brown's focus — like Bush's — was on the "substantial progress" being made by a U.S.-led coalition of troops.

Brown announced shortly after taking office that he would reduce British troop levels in Iraq. But that plan, to bring British troop numbers to 2,500 from about 4,000 starting within weeks, is now on hold until Iraqi security forces make gains in driving out militias from the oil-rich southern city of Basra.

The two displayed no daylight between them in their views on other key topics as well, including criticism of Zimbabwe President Robert Mugabe's refusal to release results of elections believed to have been won by opponents three weeks ago; frustration with the slow pace of peacekeeping help for Sudan's violent Darfur region; and belief in the need for a global deal lowering tariffs.

The British leader praised Bush's anti-terrorism leadership effusively, saying "the world owes President George Bush a huge debt of gratitude." He called the president's programs to battle AIDS and malaria in Africa "pioneering work." He labeled their session an "excellent meeting" that left the bond between the two nations "stronger than ever."

There was even gentle ribbing about whether Bush actually was going to cook the intimate dinner the two leaders and their wives shared in the evening in the White House residence.

Blair's popularity plummeted because of his support for Bush, making Brown wary up to now about forging ties that are too close. But Brown went so far as to invoke Blair's name in promising to align himself with the U.S. leader.

"As Tony Blair said, we stand shoulder-to-shoulder with the American people and with President Bush," Brown said. "And I continue to stand shoulder-to-shoulder with him in rooting out terrorism wherever we find it in any part of the world which puts freedom, democracy and justice at risk."

Even before his trip, Brown had said he hoped to strengthen ties through coordinated efforts to shore up the world economy and work on climate change.

Brown diplomatically declined to state a personal preference in the race to succeed Bush. Brown met earlier Thursday one-on-one, with Republican presidential candidate Sen. John McCain and his Democratic rivals, Sens. Hillary Rodham Clinton and Barack Obama, one of whom will be his ally come January.

But at Bush's side, he said: "It is for Americans to decide who their president is going to be."

Bush did his part too.

The president lavishly praised the contributions and honored the sacrifices of British troops in Iraq, commenting on the "brilliance" of British helicopter crews during recent fighting in support of an Iraqi offensive in Basra.

And Bush interjected when Brown was asked if the relationship is less special than it was with Blair.

"False," he said. "This is a unique relationship. It truly is. And I value my personal friendship, as well as our relationship between our countries. Look, if it wasn't a personal relationship, I wouldn't be inviting the man to a nice hamburger or something."

On Iran, Bush rejected Tehran's argument that its nuclear activities are intended only for a civilian energy program. "If that's the case, why did they have a secret program?" he asked.

Bush added that he regards Tehran as "untrustworthy" on the topic. So even if Iranian officials are telling the truth now about a benign reason for their enrichment activities, he suggested that could easily change.

"To say that well, OK, it's OK to let them learn to enrich and assume that that program and knowledge couldn't be transferred to a program — a military program — in my judgment is naive," he said.

Brown said that not only was he taking his own action to control Tehran, but supported U.S. efforts to press Iran through talks and the threat of a new, tough round of sanctions at the United Nations.

He did stress that it is important to monitor the effect sanctions are having in Iran, where inflation is high.

Bush and first lady Laura Bush greeted Brown and his wife, Sarah, at the North Portico of the White House. Mrs. Bush said while waiting for them that her husband was kidding about the hamburger. The dinner included minted pea soup, caviar, ribeye with braised endive and cherry crisp with rhubarb compote.