(AP) China's biggest state-owned oil company said Monday the board of directors of PetroKazakhstan, a Canadian company that is a major oil producer in China's neighbor Kazakhstan, has accepted a $4.2 billion takeover offer.

The takeover by China National Petroleum Corp., which requires approval by PetroKazakhstan shareholders, would add to a series of foreign oil and gas acquisitions that Beijing hopes will secure energy supplies for its booming economy.

The announcement comes about three weeks after another Chinese oil company, CNOOC Ltd. withdrew a multibillion-dollar bid for U.S. oil and gas producer Unocal Corp. after opposition by critics who said it might threaten U.S. national security.

Chinese state-owned companies have signed a multibillion-dollar string of deals in recent months to develop oil and gas fields and buy fuel supplies from countries as far-flung as Sudan, Venezuela and Australia.

The takeover of PetroKazakhstan would add closer economic ties to the growing strategic cooperation between China and Kazakhstan, which is expected to become one of the world's leading oil producers over the next two decades.

China is trying to increase its role in Central Asia, spurred in part by unease at the presence of U.S. military forces in the former Soviet region that borders Afghanistan.

CNPC is China's biggest oil producer and the parent company of PetroChina Co. Ltd., whose shares are traded on stock exchanges in Hong Kong and New York.

PetroKazakhstan is based in Canada but all of its operations are in Kazakhstan. The Canadian company says its proved and probable oil reserves stand at 550 million barrels.

PetroKazakhstan shareholders are to vote at a meeting that is expected to be held in October, CNPC said in a prepared statement, and the Canadian company's board has recommended shareholders accept it.

The CNPC offer would pay PetroKazakhstan shareholders a total of $55 per share _ $54 in cash, plus one share valued at $1 in a new company that would pursue energy deals elsewhere in Central Asia, the Canadian firm said. The offer represents a 21 percent premium over PetroKazakhstan's Friday closing share price of $45.40 on the New York Stock Exchange.