Oil giant Unocal is rethinking its dealings with a Chinese consortium after U.S.-based Chevron upped its buyout bid by $1 billion on Wednesday, July 20.

The board of directors with Unocal – America’s second largest oil company – said they’d rather see Unocal purchased by Chevron than by China’s state-run CNOOC Ltd. the Washington Post reported.

That announcement comes after Chevron upped its bid from $16 billion to $17 billion, compared to China’s $18.5 billion bid. Despite the higher foreign offer, Reuters reports that Unocal board members believe U.S. regulators would reject a sale to China based on national security concerns.

Unocal stockholders are scheduled to vote on the sale to Chevron at a meeting on Aug. 10.