The G20 group of nations are meeting in the Canadian city of Toronto, with managing the recovery from the global recession dominating the agenda.
The summit follows the smaller G8 meeting, which ended on Saturday with the world's richest countries failing to make any major breakthroughs.
Delegates at the G8 meeting faced deep divides over how to tackle the global economic crisis.
Other important issues discussed ranged from Israel's blockade on Gaza to Iran and North Korea's nuclear programmes, which were severely criticised.
The G20 intends to agree on cutting their deficits in half by 2013, Angela Merkel, the German chancellor, said on Sunday.
Al Jazeera's Imtiaz Tyab, reporting from Toronto, said that economic divisions continue to dog leaders going into the meeting.
"What we can expect from this larger grouping is whether they can get past their divisions. When it comes to global finances we are seeing a big split, particularly between the US and Europe," he said.
The US supports continued economic stimulus spending to galvanise the recovery, but European countries are facing a sovereign debt crisis that is squeezing national budgets and prompting governments to make severe cuts in spending.
Hundreds of protesters demonstrated in Toronto on Saturday against both the G8 and G20 summits.
Canadian authorities on Sunday said more than 400 people had so far been arrested on charges ranging from mischief to assaulting an officer, and police were braced for more possible trouble.
A group of people broke away from Saturday's largely peaceful demonstration, breaking store windows and burning two police cars in downtown Toronto before officers used tear gas to disperse them.
"What we saw yesterday ... is a bunch of thugs that pretend to have a difference of opinion with policies and instead choose violence in order to express those so-called differences of opinion," Dimitri Soudas, a spokesman for Stephen Harper, the Canadian prime minister, said.
"People do disagree on issues, leaders that meet all the time don't necessarily always see eye to eye all the time. But you don't see people burning up police cars and breaking windows," he added.
Source: Al Jazeera and agencies