(Refiles to correct ConocoPhillips' stock symbol in first paragraph to COP.N from COP.TO)

CALGARY, Alberta - Chinese state-owned company Sinopec plans to buy ConocoPhillips' stake in the largest project in Canada's oil sands for $4.65 billion, the richest deal yet to expand China's interest in the huge unconventional resource.

ConocoPhillips, the U.S. oil major, said on Monday it will sell its 9.03 percent interest in the Syncrude Canada Ltd project to China's top refiner in a high-priced deal due to close in the third quarter. It put the stake on the block last year.

The acquisition comes amid an investment resurgence in the Alberta oil sands as oil prices have jumped following the economic meltdown.

The deal differs from other Chinese oil sands acquisitions, as the others were early-stage projects. Syncrude has operated since 1978, and now pumps out 350,000 barrels a day.

They are obviously very active in investing, said FirstEnergy Capital Corp analyst Mike Dunn.

I had previously been under the impression that the Chinese were more interested in deploying their capital to projects and assets where it is needed to grow production, and as such I didn't think they were a likely winning bidder for Syncrude.

For ConocoPhillips, the deal is part of a two-year, $10 billion disposition program. When it first said it was putting the stake on the block last October, analysts pegged the value at $3.6 billion to $4 billion.

I think it's a transaction that the market has been expecting, so it's not necessarily a surprise, said Alain Auclair, head of investment banking in Canada for UBS. What this shows is that financial markets are working, definitely.

Shares in ConocoPhillips were up 56 cents, or 1 percent, at $55.88 on the New York Stock Exchange.

The oil sands make up the largest crude deposit outside the Middle East, a resource attracting a Who's Who of the global oil industry willing to pay extra in development costs in exchange for a secure supply in a politically stable country.

Chinese state oil companies have been expanding their presence as China seeks energy supplies worldwide to fuel its expanding economy.

Sinopec already has an oil sands stake. Last April, it bought an additional 10 percent interest in Total's planned Northern Lights project for an undisclosed price. Also in 2009, PetroChina acquired a majority interest in leases held by Athabasca Oil Sands Corp for C$1.9 billion ($1.9 billion).

Sinopec's latest deal requires approvals from governments in Canada and China. Canada recently tightened foreign investment reviews but has not rejected any oil sands transactions.

As far as regulatory concerns, I don't think it will be an issue. The Chinese are looking at a pretty friendly environment in terms of doing business in Canada, Morningstar analyst Allen Good said.

Syncrude's largest owner, Canadian Oil Sands Trust, had been speculated as a buyer of the ConocoPhillips stake. Officials at the trust, which has a 37 percent interest in Syncrude, were not immediately available for comment.

Canadian Oil Sands units were up 7 percent at C$32.78 on the Toronto Stock Exchange.

The other owners are Imperial Oil Ltd, Suncor Energy Inc, Nexen Inc, Murphy Oil Corp and Nippon Oil Corp unit Mocal Energy.

(Additional reporting by Mike Erman in New York, Anna Driver in Houston and Pav Jordan in Toronto; editing by Peter Galloway)