Czech Prime Minister Andrej Babis on Tuesday said the country's president had promised to nominate him to form a government at a Sunday meeting, shortly before the head of state was rushed to hospital.
The claim came as politicians looked for ways to end the impasse brought on by President Milos Zeman's hospitalisation just when he is required to appoint a premier following elections.
"When I talked to the president on Sunday, he said that when the moment comes, he will ask me," Babis told Czech TV.
"It is up to me to accept or refuse," he said, adding he was also ready to go into opposition.
The centre-right Together alliance narrowly won last weekend's vote ahead of the populist ANO party of billionaire Babis.
Along with another centrist alliance, Together would have a majority of 108 seats in the 200-seat parliament.
But Zeman had said before the election that he would tap the leader of a party, not an alliance, to form the next government, suggesting his old political ally Babis would go first.
Given the make-up of the new parliament, he would struggle to form a majority or continue with a minority government.
Czech media have meanwhile started to suggest names that might appear in the next government, with Together leader Petr Fiala seen as the most likely candidate for prime minister.
The hospital has said the president is in a stable condition and being treated by elite intensive care specialists.
"Unchanged, thank you, good bye," Prague military hospital spokeswoman Jitka Zinke told AFP when asked about Zeman's condition.
Local media said the 77-year-old president, who allegedly suffers from liver problems, may stay in hospital for weeks.
Zeman's spokesman Jiri Ovcacek told Proglas radio that Zeman had been visited by his family members and closest collaborators.
He said on Tuesday that information about the president's condition will be provided "continuously but sparingly".
But Senate speaker Milos Vystrcil said in a statement he would officially ask Zeman's office for more information as "we are concerned that his current condition may not allow the president of the republic to do his job."
The Senate has called a meeting of its committee for the constitution to discuss the deadlock next week.
- 'Unable to execute his official duties'? -
Under article 66 of the constitution, the two houses of parliament can adopt a resolution by a simple majority stating that the president "is unable to execute his official duties for serious reasons".
"I think it's time to start contemplating article 66," Jan Kysela, a constitutional law expert from Charles University in Prague and a secretary of the Senate committee, told AFP.
"If (Zeman's) prognosis is unfavourable for weeks ahead, it is time to think about activating the mechanism," he said.
After the resolution, the president's powers would be taken over by the outgoing prime minister and by the speaker of the new parliament, who would have the authority to appoint the next prime minister.
Babis faces charges over EU subsidy fraud and the EU's anger over his conflict of interest as a politician and businessman.
He was also named in the Pandora Papers investigation earlier this month as he had allegedly used money from offshore firms to buy property in France, including a chateau on the Riviera.