Pakistani Prime Minister Yousaf Raza Gillani sought Monday to shore up support for his embattled U.S-allied government, one day after it plunged into a new crisis when a key ally abandoned the ruling coalition for the opposition.

Gillani met with leaders of the two primary opposition parties, the Pakistan Muslim League-N and the Pakistan Muslim League-Q, in a bid to gain their support in case of a no-confidence vote against him in parliament, which could trigger the government’s collapse.

The defection on Sunday of the Muttahida Qaumi Movement, the governing coalition’s second-largest partner, deprived President Asif Ali Zardari’s Pakistan People’s Party of its parliamentary majority. That raised the prospect that federal lawmakers would oust Gillani, possibly prompting early elections.

Either Gillani’s ouster or early elections would jolt an already shaky political order in Pakistan, further distracting the weak government from its U.S.-backed fight against Islamist militants and efforts to deal with corruption, rising inflation and an ailing economy.

The MQM said it decided to quit over recent state-controlled gasoline price hikes, which have compounded the woes of a population already struggling with 15 percent inflation.

Amid rumors that factions loyal to Zardari were pushing for Gillani’s dismissal, the PPP vowed on Monday to support the prime minister.

“The prime minister is not alone; he will not be left alone,” Zardari spokesman Farhatullah Babar said. “The party stands behind him through thick and thin.”

The plans of the main opposition parties, whose support the PPP needs to maintain a clear mandate in parliament, remained unclear. Although the widely fractured opposition parties were unlikely to unite in a vote of no-confidence against Gillani, political analysts said a PPP-led minority government could face legislative paralysis — and possibly the intervention of the powerful military.

Representatives of the PML-N, led by former prime minister Nawaz Sharif, said they would discuss the party’s course at a meeting on Tuesday. But they also quashed the idea of siding with the government.

“PML-N should not be expected to rescue a government which is incompetent and corrupt,” said Chaudhry Nisar Ali Khan, the leader of the opposition in parliament.

The PPP indicated Sunday that it held out hope that the MQM would remain in the federal coalition. The MQM, though, insisted it would not, and it filed parliamentary paperwork Monday required to switch to the opposition.

Though relations between the two parties are hugely frayed, they remain in alliance in the province of Sindh, where the PPP dominates the rural areas and the MQM rules in urban areas, including the massive port city of Karachi.

The opposition parties joined together in parliament on Monday to demand a withdrawal of the gasoline price increase.

Haider Abbas Rizvi, a top MQM leader, said his party “could not bear the burden of petrol bomb.”

Special correspondent Hussain contributed from Islamabad.