A general view of the Lyondell-Basell refinery in Houston, Texas.

Saudi Aramco and its U.S. refining joint-venture Motiva Enterprises lead the race to buy Lyondell Basell Industries Houston refinery, according to three sources familiar with the matter.

An announcement of the sale by Lyondell is expected this week, the sources said.

Lyondell spokesman Michael Waldron declined on Monday to discuss a sale of the refinery.

Reuters reported on Aug. 25 that Dutch chemical company Lyondell had retained Bank of America Merrill Lynch to help with a sale of the refinery.

A company spokeswoman said in August, "the refinery may be more valuable as part of a larger refining system. We are exploring all options."