Stephen Harper spoke on the telephone with U.S. president-elect Barack Obama on Thursday to congratulate him on his election victory earlier in the week, the Prime Minister's Office said.

In a statement, the PMO described the conversation as a "warm exchange," in which the two leaders "emphasized that there could be no closer friends and allies and vowed to maintain and further build upon this strong relationship."

They touched on the upcoming G-20 leaders' summit in Washington on Nov. 15 and its importance for addressing the global financial crisis.

Earlier in the day, the prime minister said Obama's election to the U.S. presidency is an "inspiring moment," and that Canada will work with the new administration as its "most reliable ally in the world."

Harper was responding to a reporter's question why his office only issued a simple, short communiqué after the Democratic candidate was named the election winner on Tuesday night.

"Obviously, the election of the first African-American president is a tremendous and truly inspiring moment, I think, in American political history," Harper said during a press conference following a meeting with economists and business leaders in Toronto.

"And I think all of us who are maybe a little bit older — I’m getting into that category — understand why that truly is when we see the changes that have occurred in their society and our society over the past couple of generations."

Harper also said he believes Obama, who has pledged to increase America's energy independence and security, will understand that the U.S. faces "major challenges" and that Canada remains "the major source of energy and the most secure source of energy."

"We have shared challenges and we will always work in full collaboration with our ally, our most important partner," he said. "It's an era of possibility."

PM notes 'major change' in environmental approach

Harper, accused by his opponents in Parliament of siding with the Bush administration in opposing international climate-change initiatives, also described Obama's stated desire to participate in global efforts to reduce greenhouse gas emissions as a "major change."

"As I have said many times in the past … it’s almost essential for Canada to manage this problem in co-operation with the United States because we share the same economy," Harper said. "We share the same continent, and we need a partner in the matters of the environment if we want to make real progress."

He said the Canadian government viewed Obama's intention to shift more soldiers and resources into Afghanistan from Iraq as "positive, and obviously consistent with Canadian policy."

Although Harper and Obama have never met face to face, the prime minister said the two had "a good conversation" in the spring and he expected to have a chance to talk to the president-elect soon.

"I look forward to that conversation, to meeting with the senator in person."