Canadian officials have expressed interest in sending oil to China through pipelines to the western coast. Last week, Chinese National Offshore Oil Corp. moved to acquire Canadian oil company Nexen Energy.
"Giving valuable American resources away to wealthy multinational corporations is wasteful but giving valuable American resources away to a foreign government is far worse," Markey's letter read.
Geithner, as chairman of the Committee on Foreign Investment in the United States, needs to review the deal. Nexen has drilled in the U.S. waters of the Gulf of Mexico.
Markey said the Canadian company hasn't paid "a dime" in royalties for its current operations.
U.S. Sen. Charles Schumer, D-N.Y., last week issued a similar plea. Schumer said it's "rare" to have the opportunity "to put our foot down over China's refusal to play by the rules of free trade."
Their counterparts in the Republican Party last week said the Nexen acquisition shows how much the United States needs the Keystone XL pipeline.
None of the companies involved had a public reaction to U.S. lawmakers' concerns.