World leaders had initially promised to help stabilize the Chernobyl site last year at the G8 summit in Ontario's Muskoka region.

"Our Government remains committed to helping the people of Ukraine deal with the aftermath of the Chernobyl nuclear accident," Harper said in France.

"It is fitting, on the 25th anniversary of this tragedy, to join the international community in closing this sad chapter once and for all."

The funds announced Thursday bring Canada's contribution to the project to $105 million. The work is expected to be completed by 2015.

Also on Thursday, Harper and U.S. President Barack Obama were expected to take some time out from the G8 schedule for a bilateral meeting on perimeter security.

The Prime Minister's Office said the meeting would likely advance talks on a unified border security system for the continent that have been underway since February.

The hope is that such a pact would tighten security for people and goods entering the continent, but allow Canada-U.S. border points to boost the flow of goods and vehicles travelling across the 49th parallel.

Sources say the agreement would include joint border inspection agencies, relocation of U.S. food inspectors agents to Canadian plants and vice versa, greater sharing of intelligence, and harmonizing regulations on everything from food to manufactured goods.

Harper also met with Japanese Prime Minister Naoto Kan and British Prime Minister David Cameron on Thursday.

CTV's Daniele Hamamdjian, who is travelling with the prime minister, said a hot topic at the G8 is the recent uprisings across the Middle East and North Africa.

The Group of Eight leaders were expected to discuss what means of support they may offer to pro-democracy movements, though the meetings were not intended to be "a pledging session" for the countries involved in the so-called Arab Spring, Hamamdjian said by phone from Deauville.

"The main focus is to find out how they're going to assist and how to organize any assistance for Egypt and Tunisia," she said.

Prime Minister Stephen Harper said he expects any aid delivered to the North African countries would be through various multilateral channels.

"We've upped our capital contributions to the various multilateral development banks that will assist in this regard," Harper told reporters Thursday night. "I think that's the best way to get a co-ordinated international response."

He said he doesn't think debt forgiveness is a reality for the Middle East.

"Canada's debt in this case is quite long term so debt forgiveness really would not be a particularly useful tool in terms of what we could do in this region," he said.

While discussions about the Arab world took place at a dinner on Thursday evening, interim prime ministers from Tunisia and Egypt will also meet with the group on Friday for a special session.

The Friday session will be aimed at identifying the most critical needs of Tunisia and Egypt as they move toward elections. Representatives from the International Monetary Fund and the World Bank will give G8 leaders their view on what steps need to be taken to modernize the economies of the two countries.

G8 leaders are expected to focus on several other pressing issues, including nuclear safety, climate change and the state of the global economy, Hamamdjian said.

The maternal and child health initiative, which Harper spearheaded during the G8 summit last year, is also on the agenda. But it is "falling off the radar," Hamamdjian told CTV's Power Play.

Gordon Smith, a former G7/G8 sherpa -- an emissary for Canada -- and a distinguished fellow at the Centre for International Governance Innovation, said that with a new Conservative majority government in Ottawa, Canada may now have an opportunity to play a larger role at events like the current G8 summit.

"The reality is the Harper government has not been particularly active over the past five years" outside of Canada, except on the economic front, Smith said from Victoria. "Now Prime Minister Harper has the opportunity, with his colleagues, to play a major role on the international scene."

The recent departure of former IMF managing director Dominique Strauss-Kahn, who is facing criminal charges in the United States, will also be a topic of discussion at the summit on Friday.

While Strauss-Kahn's successor has yet to be selected, there is at least one high-profile candidate seeking his former position: French Finance Minister Christine Lagarde has announced her candidacy for the IMF job and she has so far garnered support from a number of powerful nations in Europe.

Canadian Finance Minister Jim Flaherty recently said Lagarde was one of at least "two strong, qualified candidates" seeking the IMF job.

The other was Augustin Carstens, the U.S.-educated chief of the central bank in Mexico, who previously served as the deputy managing director of the IMF.

Carstens' possible candidacy for the top IMF job could draw the backing of emerging economies that favour seeing a non-European lead the organization for the first time in its history

With files from The Associated Press and The Canadian Press