Adds Enterprise securities filing with copy of letter from Commerce Department

By Karen Freifeld

June 25 (Reuters) - The U.S. sent letters to Enterprise Products EPD.N and Energy Transfer ET.N on Wednesday informing the companies they could load ethane on vessels destined for China but could not unload the ethane in China without authorization, according to a person familiar with the matter and copy of one letter.

The letters from the U.S. Department of Commerce follow a licensing requirement imposed several weeks ago on the companies' exports of ethane to China, which halted shipments and led to vessels anchoring in or hovering around the U.S. Gulf Coast.

The letters may signal the U.S. preparing to lift restrictions imposed on exports to China in late May and early June, as the U.S.-China trade war shifted from retaliatory tariffs, to curbs on each others supply chains. With China granting rare earth export licenses to some firms and saying it would speed up the approval process, the U.S. now appears close to permitting ethane exports to China.

Still, the companies are highly unlikely to risk loading the ethane on vessels and sending them on their way, the person familiar with the matter said. If the vessels make their way to China, it may be difficult to stop them from offloading the ethane and the companies could face penalties of up to twice the value of the shipment if they do.

A copy of the letter seen by Reuters and later released by Enterprise Products said, "This letter authorizes Enterprise Products to load vessels with ethane, transport and anchor in foreign ports, even if... to a party located in China," the letter said. "However, Enterprise Products may not complete such export... to a party that is located in China," without further authorization.

The securities filing with the letter did not include additional comment.

Enterprise Products and Energy Transfer, two of the top U.S. ethane producers and exporters, did not respond to requests for comment. About half of all U.S. ethane exports go to China, where it is used by the petrochemical industry.

The U.S. Department of Commerce also did not immediately respond to requests for comment.

The ability to load and begin transporting ethane could relieve congestion at ports along the U.S. Gulf coast, where vessels have been stalled.

Since May 23, the U.S. imposed new restrictions on exports to China of everything from ethane and chip design software to jet engines and nuclear plant parts.

(Reporting by Karen Freifeld; Editing by Chris Sanders and Chizu Nomiyama)

((karen.freifeld@thomsonreuters.com; +1(646) 223-6921;))