HUNTSVILLE, Ontario — As world leaders gathered to deal with the aftermath of the global financial crisis, President Barack Obama boasted about a congressional compromise on overhauling the U.S. banking system and called for an international effort to prevent future economic meltdowns.

But Obama was still facing major obstacles in convincing a balky Congress to provide more money to fight high unemployment and many countries were resisting Obama’s appeals for continued stimulus spending to support the global economy. They were moving in the opposite direction to raise taxes and cut government programs out of fears of a Greek-style debt crisis.

After meeting through the night in Washington, congressional negotiators cleared the financial overhaul proposal with the help of an administration-brokered compromise on derivatives trading.

The agreement was certain to be a major discussion point as Obama and other leaders of the Group of 20 major economies gathered for three days of talks in Canada. Those discussions were beginning today with a session at a Huntsville, Ontario, resort, a three-hour drive north of Toronto in Canada’s Muskoka lakes region.

“We need to act in concert for a simple reason: This crisis proved and events continue to affirm that our national economies are inextricably linked,” Obama said on the White House lawn before leaving for Canada. “At the G-20 summit this weekend, I’ll work with other nations not only to coordinate our financial reform efforts but to promote global economic growth.”

White House spokesman Robert Gibbs told reporters on Air Force One that Obama had taken a number of bold steps to deal with the financial crisis since taking office last year and now “he leads the world in financial reform.”

Leaders of the Group of Eight major industrial nations – the United States, Japan, Germany, France, Britain, Italy, Canada and Russia – were meeting today to discuss a range of initiatives to alleviate global poverty.

Those discussions were to move back to Toronto on Saturday and Sunday for talks with the larger G-20 group which includes the rich countries and major developing nations such as China, Brazil and India.

The G-20 group represents 85 percent of the global economy and the United States wants this group to endorse the outlines for global financial reform to eliminate the threat that banks facing tougher regulations in one jurisdiction will move their operations to countries with more lax rules.

Even before the summit began, the leaders engaged in a series of dueling letters and interviews that exposed their conflicts.

A key discussion point for the G-8 was a proposal being promoted by Canadian Prime Minister Stephen Harper, the summit host, to bolster support for maternal and child health care in poor nations.

The G-8 was also holding an outreach session with leaders of seven African nations. Nigerian President Goodluck Jonathan said the G-20 should be expanded to include more African nations. At present, only South Africa is a member.

“If African nations have challenges, the West also pays for it,” Jonathan said in an interview in Toronto’s “The Globe and Mail.” Nigeria, Africa’s most populous country, would be a likely candidate for inclusion if the G-20 is expanded.

In an opinion piece the newspaper published today, new British Prime Minister David Cameron said he was determined to make his first international summit a success.

“Too often, these international meetings fail to live up to the hype and the promises made,” Cameron wrote. “A lot of money is spent laying them on. Host cities disrupted for days, even weeks. The cavalcades roll into town.”

Cameron said Britain’s main priority at the meeting was to hear each country provide details about plans for getting their “national finances under control.”

The G-8 was also scheduled to spend time over dinner Friday night discussing the nuclear standoffs with Iran and North Korea and seeking consensus on ways ahead.

The U.S. and its allies will be looking to convince China to support U.N. Security Council action to hold North Korea accountable for the sinking of a South Korean warship in March.

On Iran, the U.S. and European nations will push other major powers to join them in imposing tough new sanctions on Tehran over its suspect nuclear program, building on expanded Security Council measures adopted earlier this month.

But China and Russia only reluctantly supported the sanctions, and have balked at new unilateral steps against Iran, saying any measures should not exceed those called for by the Security Council.

The House-Senate conference committee agreement on financial overhaul, which the administration hopes can be passed by Congress and on Obama’s desk by July 4, represented a welcome triumph for a White House that has had a tough two months dealing with the worst offshore oil spill in U.S. history and a Congress increasingly worried about soaring U.S. deficits.

On Thursday, solid Republican opposition caused the defeat of legislation that would have provided billions of dollars for job creation and extended benefits for unemployed people.

Other G-20 leaders have not signaled much support for Obama’s warnings that countries should not pull back their stimulus efforts too quickly.

Britain, Germany, France and Japan have all unveiled deficit-cutting plans. Canada’s Harper was urging the countries to agree to concrete deficit-reduction goals as a way of restoring investor confidence following the turmoil caused by the Greek debt crisis.

Toronto’s downtown core resembled a fortress with a big steel and concrete fence erected over several blocks to protect the summit site. Canadian police patrolled the Lake Ontario waterfront from boats and jet skis with the number of security forces protecting the summit meetings estimated to total 19,000, drawn from all over Canada.

The G-20 leaders’ summits began in the fall of 2008 in response to the global economic crisis that struck with fury after the collapse of Lehman Brothers, a major U.S. investment bank.

At that time, the leaders joined to assemble multibillion-dollar support packages to restart economic growth and financial rescue efforts to rescue a froze global banking system.

But now that the banks are back from the brink and the world’s economies are growing again, unity is proving more elusive.