The UK’s biggest tour operator had previously cancelled all trips up to June 11.
It has also suspended its Marella Cruises sailings up to July 30.
It comes after budget airliner easyJet announced it planned to cut around a third of its workforce due to the fall in passenger demand.
Tui said in a statement that it has extended the suspension of holidays “due to the ongoing travel restrictions”.
Rival tour operator Jet2holidays has also suspended its holidays up to June 30.
A 14-day quarantine for international arrivals is due to begin in the UK on June 8.
The Foreign and Commonwealth Office (FCO) has advised against all but essential international travel since March 17.
Major UK tour operators will not run trips until the FCO changes its position.
Health Secretary Matt Hancock appeared to be more optimistic than in the past when asked about the prospect of people being able to go on holiday this summer.
He told BBC Radio 4’s Today programme: “I think the answer is let’s see where we get to.”
Mr Hancock had previously commented that “big, lavish international holidays” were “unlikely” to be possible this summer.
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