Protesters carrying images of G8 summit leaders march through the streets of Sapporo, Japan, on Saturday. (Shuji Kajiyama/Associated Press)

The head of the European Union's executive says the Group of Eight summit leaders may be ready to step up promises to cut greenhouse gas emissions when they meet on the northern Japanese island of Hokkaido this week.

Commission President Jose Manuel Barroso said on Sunday that leaders of wealthy countries in the group will be "working for real commitments" on the issue.

Leaders from the G8 — which includes the United States, Japan, Russia, Germany, France, Britain, Italy and Canada — will gather for a three-day meeting in Toyako Hot Spring Village near Sapporo, starting Monday.

Prime Minister Stephen Harper was among world leaders who arrived in Japan Sunday for the summit of top industrialized countries.

Talks during the summit will focus on issues including global warming, soaring oil prices and possible sanctions against Zimbabwe. The host country Japan has put talks on climate change high on the agenda.

Barroso said he and his European colleagues will be pushing for a declaration that the G8 will take the lead in efforts to halve worldwide emissions by 2050, reinforcing a pledge taken at the previous summit in Germany last July.

The EU group will also determine whether it can win a mid-term commitment for reducing emissions by 20 per cent from their 1990 levels by 2020, he said.

Baird foresees no firm targets

Environment Minister John Baird told journalists aboard the prime minister's Airbus that he doubts the G8 leaders will leave Japan with firm reduction goals in hand.

Canada, the U.S. and Russia have all said there's no point in large, developed economies pledging to meet tough targets unless developing countries such as China and India agree to the same goals.

Hundreds of anti-globalization protesters marched Sunday through Sapporo, the closest major city to the summit site, under the watchful eyes of a heavy police presence. The march ended peacefully.

During a protest demonstration in the city on Saturday, there were four arrests and a brief scuffle with police as officers smashed the window of a van that refused to stop amid the protest.