The Caribbean Hotel and Tourism Association (CHTA) wants Tui to pay hotels for services provided in the first quarter of 2020.
It made an initial appeal in April, when it said the average amount owed per property by all operators was $219,000.
"Most tour operators honoured their obligations, and we’ve been pleased to see that a number of those who had delayed reimbursements have settled since our appeal in April," said Frank Comito, CHTA’s chief executive and director general.
"But millions of dollars in reimbursements remain obligated and are jeopardizing the hoteliers’ survival and ability to meet obligations, like taxes and labour expenses, because of the holdout by Tui and several other tour operators."
In a letter to Andrew Flintham, managing director of Tui’s United Kingdom and Ireland operations, Comito said he wanted the company to join its competitors in settling debts to Caribbean hotels “whose survival is under threat”.
Comito said the response from Tui “regrettably provided no immediate redress for financially impacted Caribbean hotels”.
The CHTA also described efforts by Tui to amend contracts to “onerous” payment terms tied to receiving the Q1 payments as "unreasonable and untenable".
It said it noted the public statement of apology Flintham recently made to clients awaiting cancellation reimbursements.
"While a similar sentiment would be appropriate to your loyal and longstanding partner hotels in the Caribbean ... we urge your support in expediting the reimbursement of these obligations."
Comito added: "This has become a matter of survival for many small to medium-sized hotel operators in the Caribbean, many of which are independent and locally owned."
Tui told TTG: "We have long-lasting and very successful relationships with our partners in destinations which remain intact during these unprecedented times.
"Tui has put a number of measures in place to return the business back to normal operations in the wake of the Coronavirus crisis. For the season which ended in March, Tui is currently liaising with all its partner hotels to discuss a payment plan for the remaining amount.
"We have been preparing to re-start travel operations as travel restrictions in Europe gradually are resuming and our local teams are in direct contact with all our partners in the destinations.”
