Rep. Edward Markey (D-Mass.) wants Treasury Secretary Timothy Geithner to place conditions on the Chinese oil company CNOOC Ltd.’s acquisition of a Canadian firm that drills in American waters, becoming the second senior Democrat to seek U.S. intervention in the deal.

Markey, in a letter to Geithner Monday, said the state-owned CNOOC’s proposed $15 billion purchase of Nexen Inc. should be conditioned on the parties agreeing to pay royalties on Gulf of Mexico oil leases that currently allow royalty-free production.

“I believe this merger could lead to a massive transfer of wealth from the American people to the Chinese government, and I strongly urge you to block this proposed transaction until, at a minimum, parties to the merger agree to pay royalties to the U.S. taxpayer on all oil produced off American shores or relinquish any ownership interests in these leases,” Markey stated in the letter sent Monday to Geithner.