World leaders wave during their official photo at the G-20 Summit on Sunday in Toronto. In the front row from left are South Korean President Lee Myung-bak, Canadian Prime Minister Stephen Harper, President Barack Obama of the United States, King Abdullah of Saudi Arabia and French President Nicolas Sarkozy.

Toronto ? Wary of slamming on the stimulus brakes too quickly but shaken by the European debt crisis, world leaders pledged Sunday to reduce government deficits in richer countries in half by 2013, with wiggle room to meet the goal.

Leaders of 20 major industrial and developing countries generally sided with cutting spending and raising taxes, despite warnings from President Barack Obama that too much austerity too quickly could choke off the global recovery.

“Serious challenges remain,” they cautioned in a closing statement. “While growth is returning, the recovery is uneven and fragile, unemployment in many countries remains at unacceptable levels, and the social impact of the crisis is still widely felt,” according to the document from the Group of 20 major industrial and developing nations.

Obama told a news conference he was satisfied with the outcome, saying he recognized that countries had to proceed at their own pace in either emphasizing growth or budget austerity.

“We can’t all rush to the exits at the same time,” Obama said after three days of economic summitry.

Summit participants navigated a careful course between Obama’s emphasis on growth and fellow leaders such as German Chancellor Angela Merkel who advocated spending cuts and even tax increases.

“Advanced economies have committed to fiscal plans that will at least halve deficits by 2013 and stabilize or reduce government debt-to-GDP ratios by 2016,” according to the statement. The gross domestic product, or GDP, measures the value of all goods and services, and is considered the best gauge of economic health.

At the same time, the statement called for following through on “existing stimulus plans,” heeding Obama’s concerns.

Japan was given an exemption from meeting the debt targets because of years of a stagnant economy, and the fact that its huge debt is largely owned by Japanese and not overseas investors.

Canadian Prime Minister Stephen Harper, the summit host, told reporters that deficit reduction “is not an end in itself” and that there is “an ongoing role for stimulus in the short term.”

As the summit wrapped up, conditions on the streets of Canada’s biggest city remained tense.

Police, responding more aggressively than the day before, raided a university campus and rounded up protesters in an effort to quell further violence after youths rampaged through the city the night before, smashing windows and torching police cruisers. Police said they arrested more than 600 demonstrators.

Harper blamed “thugs” for the violence and suggested the destruction and fires on the streets justified the $900 million that Canada spent for summit security.

World leaders also took note of the devastating oil spill in the Gulf of Mexico in their statement, which recognized “the need to share best practices to protect the marine environment, prevent accidents … and deal with their consequences.”

The April 20 explosion on the BP-leased Deepwater Horizon rig unleashed the worst offshore oil spill in U.S. history. BP is London-based and the disaster has contributed to strains between the U.S. and Britain.