World leaders on Wednesday weighed a huge aid package for Africa and new plans for tackling global warming as Iraq war allies President Bush and British Prime Minister Tony Blair (search) found themselves advocating rival positions.

Blair, buoyed by the decision to award London the 2012 Olympics (search), pledged to keep pushing for more aid to combat poverty in Africa and global warming, the two issues he has made the focus of this year's meeting but both goals that are more ambitious than those embraced by Bush.

Police battled thousands of protesters on the outskirts of town as the leaders of the United States, Japan, Germany, France, Britain, Italy, Canada and Russia gathered for their annual economic summit.

Leaders brought a variety of proposals and, this year, shared center stage with Irish rock star Bono (search), the lead singer of U2, who heavily lobbied some of the world's richest nations to do more for Africa.

Blair, the meeting host and first to arrive, said he was "prepared to hold out for what is right" on his agenda as summit partners followed him to a heavily fortified golf resort.

Russian President Vladimir Putin (search) is seeking the group's support a wider role for the United Nations in Iraq and may propose a possible exit timetable for the United States, the Kremlin said.

Bush, unpopular in Europe, defended his handling of Iraq and treatment of prisoners at Guantanamo. He backed less Africa aid than Blair sought, and leveled fresh criticism at the Kyoto treaty on global warming.

In a brief visit to Denmark before flying here, Bush acknowledged his unpopularity in Europe.

"I understand that people aren't going to agree with decisions I make. But my job is to make decisions that I think are right, and to lead," Bush said at a joint news conference with Danish Prime Minister Anders Fogh Rasmussen, a key ally on Iraq.

Bush also said he recognized that human activity had contributed to climate change and a warmer earth — a concession from an earlier position that the jury was still out on such a connection.

But he stood by his rejection of the Kyoto treaty on global warming, calling instead for more cooperation on cleaner fuels.

"Kyoto didn't work for the United States and it frankly didn't work for the world. The reason it didn't work for the world was that developing nations weren't included," Bush said. The United States is the only G-8 member to not ratify the agreement, which took effect in February.

Faryar Shirzad, a top Bush foreign policy aide, told reporters aboard Air Force One that final touches were being made on a summit statement for release later in the week that would unanimously emphasize "common ground" on climate control — without detailing remaining differences.

He said an effort was under way to produce such consensus-building statements on a variety of topics.

Bush and his wife, Laura, arrived in Scotland hours before the summit opened with a dinner for G-8 leaders hosted by Britain's Queen Elizabeth. The last leg of the journey, from the airport in Glasgow, was by helicopter.

As part of the African agenda, Bush, Blair, German Chancellor Gerhard Schroeder and Canadian Prime Minister Paul Martin held separate meetings with Bono.

Blair has challenged G-8 countries to double aid to Africa to $50 billion by 2010, from the current $25 billion.

"A lot has been accomplished but there is no sense that a real deal, a $50 billion number, we are not there on that," Bono said, speaking of Blair's goal.

Blair also made a joint appearance with Bob Geldof, organizer of last weekend's Live 8 concerts that were held to pressure G-8 leaders to do more to fight poverty and disease in Africa, and Bono.

"You've got to be prepared to hold out for what is right," Blair said when questioned about reports that Britain was preparing to scale back its demands on support for Africa and climate change in the face of U.S. opposition — and to help present a united front by summit's end.

"Three billion people are urging you to take it all the way," Geldof told Blair, referring to the number of people organizers have estimated either attended or watched the weekend concerts on television.

Leaders' aides met behind closed doors on Blair's top issues. Besides his call for doubling aid to Africa, Blair also wants member nations to increase giving for all foreign aid to the equivalent of 0.7 percent of national incomes by 2015.

Bush, after initially resisting Blair's call, announced last week that he would seek to double U.S. aid by 2010, to $8.6 billion from $4.3 billion last year. But he opposes Blair's 0.7 percent target.

Anti-poverty activists said Bush's goal of $8.6 billion fell about $6 billion short of what is needed from the United States to meet Blair's $50 billion target.

Bush also showed he is devoting considerable attention to a looming domestic decision, the naming of a Supreme Court justice — the first of his presidency — to succeed the retiring Sandra Day O'Connor.

White House spokesman Scott McClellan announced here that Bush had recruited former Republican Sen. Fred Thompson of Tennessee, who plays the role of a district attorney on NBC's "Law & Order," to help shepherd the nominee through the Senate confirmation process.

On treatment of detainees at the U.S. facility in Guantanamo Bay, Cuba, Bush said Fogh Rasmussen, the Danish prime minister, had raised the issue himself, "concerned about what the situation on Guantanamo says about America and our view of liberty."

Bush said he told the Danish leader the prisoners "are well-treated ... There's total transparency. The International Red Cross can inspect any time, any day."

Once U.S. courts rule on whether detainees should be tried in civilian courts or military tribunals, "then we'll proceed forward with giving people fair and open trials," he said.