Malawi's president has given parliament two days to agree a budget or he says he will close it down.
Mr Mutharika's row with his former party could paralyse the country
Bingu wa Mutharika said opposition MPs were playing "games with the lives of the people" by not meeting to seriously discuss the long-delayed budget.
President Mutharika leads a minority government after he left the party on whose ticket he was elected in 2004.
Opposition MPs are refusing to discuss the budget unless MPs who switched to the president's party are expelled.
Earlier, the finance minister told the BBC that closed-door talks between the government and opposition may be the only way to end the row over the budget.
The government says key state services and international aid contributions are at risk if the budget is not approved.
"I am giving them two days, and if today and tomorrow they do not start discussing seriously the budget, I am closing down parliament," Mr Mutharika said in a speech on national radio.
"I don't want anybody to say this is undemocratic. They are the ones who are not democratic because they want to deny the whole country of development," he continued.
The president reminded his listeners that the budget session had started on 21 April.
"Nearly four months discussing the budget - there's no parliament on this earth that will discuss the budget for four months. So I'm saying the opposition is irresponsible," he said.
The speaker ordered parliament to start debating the budget again on Tuesday afternoon, but only pro-government MPs have been speaking.
Analysts say the row could topple the government, which has so far insisted that the budget is approved before the question of expelling MPs is addressed.
The BBC's Raphael Tenthani in Malawi says the deadlock is likely to be a cause for concern to international donors who contribute 40% of the country's budget.
Finance Minister Goodall Gondwe had earlier hinted at possible talks.
Mr Mutharika (back) was chosen by his predecessor Bakili Muluzi (front) but the pair have since fallen out
"We realise as a government that there's a political impasse," he said about the six-week dispute.
"Probably it would not be discussed and resolved in the chamber, it may need to be done behind doors," Mr Gondwe told the BBC's Network Africa programme.
Prominent religious leaders and civil society activists have also been urging talks, our reporter says.
The political impasse began in June, when the Supreme Court ruled that the speaker of parliament can expel MPs who switch parties.
Most members of President wa Mutharika's party were elected on the ticket of the former ruling party, the United Democratic Front (UDF).
Mr Mutharika also won elections for the UDF, but left to set up the Democratic Progressive Party (DPP) - accusing UDF officials of blocking his anti-corruption drive.
Analysts say should the speaker expel the floor-crossing MPs, it could take six months to organise all the by-elections which would ensue.