Parliament has been unable to meet since December
The twin-island nation's two main political parties failed for a second day on Saturday to elect a speaker of the house, a move that has kept parliament from meeting since December.
Local reports say Mr Manning spoke of the possibility of fresh elections by September or October if a budget had not been passed by then.
His government cannot now pass any legislation requiring parliamentary approval, but parliament could be reconvened if an agreement was struck within the six-month period before elections must be held.
Mr Manning said he would make another attempt to elect a speaker, but gave no details of when that might happen, reports Reuters news agency.
Rivalry
The political deadlock reflects bitter rivalry between the two main political parties, in a country where voters' loyalties are largely determined by ethnic origin.
Until last December, the governing party was Basdeo Panday's United National Congress (UNC), which draws most of its support from people of Indian descent.
After the election, it ended up with 18 seats in parliament - as did the People's National Movement (PNM), which is supported mainly by Afro-Trinidadians.
President Arthur Robinson resolved the crisis by appointing Mr Manning as the new prime minister, but Mr Panday has since refused to co-operate on electing a new speaker of the house, saying President Robinson was wrong to appoint Mr Manning.
Mr Panday told reporters on Saturday that if Mr Manning could not demonstrate he had a majority support in parliament, he should call fresh elections.