Canada's prime minister is urging the world's advanced economies to halve their deficits by 2013. Prime Minister Stephen Harper, the host of next week's Group of 20 summit, said in a letter to leaders that they should agree to halve deficits by 2013 and stabilize government debt-to-GDP ratios, or put them on a downward path by 2016. Harper spokesman Dimitri Soudas released the letter on Friday. Canadian Finance Minister Jim Flaherty told The Associated Press on Thursday that the G-20 hopes to announce an agreement on deficit reduction targets at the June 26-27 summit in Toronto. Harper's letter said the targets are meant as a minimum requirement and that some countries, if they can, should move faster. US President Barack Obama released a letter appealing to the world's major economies not to waver in their efforts to support a sustained rebound. Obama signaled that countries in Europe should not withdraw the stimulus too quickly. Harper said leaders from industrially advanced countries need to reaffirm their intent to follow through on delivering existing stimulus plans, but said at the same time they must send a clear message that as they expire they will focus on reducing their deficits. Many European nations are moving to attack high deficits in an effort to calm global financial markets which have stumbled in recent weeks over concerns that Greece or other highly indebted nations could default on their loans. Banks should prepare for “comprehensive and radical” reforms to be announced by G20 leaders at upcoming summits, Canada's central bank chief said. “The G20's agenda to reshape the global financial system is comprehensive and radical,” Bank of Canada Governor Mark Carney said in a speech to international securities regulators. “The time for debate and discussion is drawing to a close,” he added. “G20 leaders have mandated a series of reforms to put the global financial system on a more solid footing.”