David Cameron is to travel to Canada for his first summits of the G8 and G20 groups of major world powers as Prime Minister.
The three days of talks will focus on the global recovery from recession, as well as banking reform, overseas aid, peace and security.
And Mr Cameron will have his first one-on-one talks with US President Barack Obama as PM on Saturday, when the BP oil spill and the situation in Afghanistan are likely to be on the agenda.
The summits come against the backdrop of austerity measures being taken across Europe - including the £40 billion package of tax rises and spending cuts in Tuesday's UK Budget - as the continent struggles to prevent the sovereign debt crisis spreading from Greece.
The measures could put Europe at odds with the US, where Mr Obama is taking a more cautious approach to paying off debts built up during the financial crisis.
In an open letter last week, Mr Obama warned G20 leaders to learn from the "mistakes of the past when stimulus was too quickly withdrawn and resulted in renewed economic hardships and recession".
Downing Street has played down any suggestion of a clash with the White House, pointing out that Mr Obama also stressed that it was for each country to develop a fiscal policy appropriate to its own circumstances.
Mr Cameron is due to visit Halifax, Nova Scotia, where he will board the HMS Ark Royal, which is taking part in an international fleet review as part of the Canadian Navy centennial celebrations.
He will then fly on to Toronto for Friday's opening of the G8 summit in the nearby resort town of Deerhurst.
The G8 leaders - Mr Cameron, Mr Obama, Canadian Prime Minister Stephen Harper, German Chancellor Angela Merkel, French President Nicolas Sarkozy, Russian President Dmitri Medvedev, Italian PM Silvio Berlusconi and Japanese PM Naoto Kan - will by joined by African leaders to talk about aid, and by heads of government from Colombia, Haiti and Jamaica to discuss international crime and security.