NEW YORK - Devon Energy Corp said on Monday it plans to sell its Gulf of Mexico and international assets and focus on its onshore fields in the United States and Canada.

It said it expects after-tax proceeds of $4.5 billion to $7.5 billion from the sales.

The sales will start in the first quarter of 2010 and are expected to be completed by the end of the year, the company said, with proceeds directed to its onshore portfolio and debt retirement.

We do not believe that the value of our high-quality Gulf and international assets is being adequately reflected in our stock price, Devon Chairman and Chief Executive Officer Larry Nichols said.

The fields represent about 7 percent of Devon's expected year-end 2009 reserves of 2.8 billion barrels of oil equivalent, the company said.

Devon owns more than 9 million acres in international assets, most of which are undeveloped. Those properties are Azerbaijan, Russia, Brazil and China.

In the Gulf of Mexico, Devon holds nearly 1.5 million acres, of which about 87 percent is undeveloped. The company has 662 producing wells and owns interests in some of the region's best potential plays in the newly discovered in the deepwater lower tertiary trend.

Shares in Devon, which have risen 3.2 percent so far this year as of Friday's close, added 3.3 percent in premarket trade to $70.00. (Reporting by Matt Daily; editing by John Wallace, Dave Zimmerman)