Oct 19 (Reuters) - U.S. group DraftKings must decide on Tuesday whether to make a formal offer for Entain , potentially kicking off a $22-billion-plus bid battle for the British gambling firm. Shares in Entain, which hit a record high late September after it received a $22.4 billion buyout proposal from DraftKings, have been bolstered by speculation the firm’s U.S. partner MGM could also make an offer. MGM failed in its attempt to buy the owner of Ladbrokes and Coral betting shops earlier this year for $11 billion. After DraftKings’ bid, MGM said any deal that would make Entain a competitor in the United States would require its consent. DraftKings was set Tuesday’s deadline for making a formal offer by Britain’s takeover regulator. (Reporting by Muvija M in Bengaluru Editing by Mark Potter)