SYDNEY, Australia (CNN) -- Australian opposition leader Kevin Rudd greeted jubilant supporters Saturday night, as he promised changes in environmental, education and workplace policies as Australia's new prime minister.

Labor Party leader Kevin Rudd has promised to start withdrawing Australian troops from Iraq.

"I will be a prime minister for all Australians," the head of the center-left Labor Party told the cheering crowd. "Let us be the generation that seizes the opportunity of today to invest in the Australia of tomorrow. That's the mission statement we have as the next government of this country."

"I want to do it with all of us working together," said Rudd, 50.

In his concession speech, Prime Minister John Howard told supporters that he leaves government with Australia "stronger and prouder and more prosperous than it was 11 and a half years ago."

With less than 75 percent of the vote counted, the Labor Party has won 83 of the 150 seats in Parliament, a net gain of nearly two dozen from the last election, according to the country's Web site results. Watch as Rudd calls for a "new page to be written" »

Labor garnered about 53.41 percent of the vote, according to the Web site.

Labor's victory over Howard's center-right Liberal-National coalition ends Howard's quest for a fifth term. With nearly 12 years in office, he is Australia's second-longest serving prime minister.

In addition, with one polling place remaining to return results, Howard looked set to lose his suburban Sydney constituency seat to Labor member Maxine McKew, a former television journalist.

Howard, 68, has been a staunch supporter of President Bush's decision to go to war in Iraq.

Rudd has said he would immediately begin talks with the Bush administration and the Iraqi government about withdrawing Australia's 550 combat troops from Iraq by mid-2008. He has said Australian troops would remain in Afghanistan.

Also in opposition to Howard and Bush -- the only leaders of industrialized nations not to ratify the Kyoto agreement on greenhouse gas emissions -- Rudd has said he would seek its ratification.

Bush called Rudd and Howard on Saturday evening, said National Security Council spokesman Gordon Johndroe.

"The president and Prime Minister-elect Rudd both said they look forward to working together to strengthen even further the U.S.-Australia relationship," he said.

"The president told Prime Minister Howard he appreciates his friendship and his strong leadership over the past seven years they have worked together, which has resulted in a stronger U.S.-Australia alliance." E-mail to a friend

CNN's Kathleen Koch and Hugh Riminton contributed to this report.

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