The U.S. and Vietnamese governments reached agreement in October. Congress now has 90 days to review it. If lawmakers do nothing, the deal will take effect.
The "123 agreement," approved by Obama on Monday, allows U.S. firms into Vietnam's civilian nuclear power market. Russian and Japanese companies are already planning to build reactors there.
Under the U.S. agreement, Vietnam is committing to rely on the international market for its nuclear fuel supply rather than enrich uranium or reprocess plutonium itself.
Some lawmakers have expressed concern over the terms of the agreement and over Vietnam's human rights record.