HOUSTON, Oct 17 (Reuters) - Exxon Mobil Corp (XOM.N) on Sunday told workers at its Beaumont, Texas, refinery their six-month lockout will end if they ratify the company"s contract offer or remove the United Steelworkers union (USW) as their representative. "As we have told the Union, the conditions which would end the lockout remain the same: the company will end the lockout when we have a signed, ratified agreement," Exxon said in a message posted on-line. "This has not changed, and anything said to the contrary is untrue. Additionally, if employees were to decertify, the company would return employees to work." Decertification is the process to remove a union from representing employees at a given location. The U.S. National Labor Relations Board (NLRB) is reviewing a petition signed by at least 30% of the locked-out workers that could lead to a vote to decertify USW Local 13-243 in Beaumont as their representative. No date for a vote has been set. read more Workers at the 369,024 barrel-per-day (bpd) Beaumont refinery and adjoining lubricant oil plant, which makes Mobil 1 motor oil, are scheduled to vote on Tuesday on the company"s contract offer. Bryan Gross, USW international representative, said the company chose to begin the lockout on May 1. "The company asked, "What has the union done?" The union has helped with groceries, assisted with bills, and is now providing health insurance for all of the "world-class employees" at a multi-billion dollar oil company put on the street instead of bargaining in good faith for a fair contract," Gross said on Sunday. The USW has urged workers at the refinery to reject the contract offer in Tuesday"s vote. NL1N2RA32R The union filled a complaint with the NLRB in June alleging the purpose of the lockout was to remove the union. Exxon said it began the lockout to prevent the disruption of a possible strike.