(Corrects paragraph 4 to say “total offer can increase to as much as $19.51 per share” and clarifies break-up fee condition) (Reuters) -U.S. investment firm Starwood Capital Group on Wednesday confirmed it sweetened its buyout bid for Monmouth Real Estate Investment Corp to $1.86 billion. Starwood raised its bid for Monmouth to $18.88 per share from $18.70 apiece. Monmouth said last week it had received an unsolicited acquisition proposal from “a large private investment firm”.