Thailand's premier called Sunday for a swift end to mass anti-government protests after two more people were killed, saying he had a back-up plan to solve the crisis if demonstrators refused to disperse.

Prime Minister Abhisit Vejjajiva demanded the opposition "Red Shirts" give a "clear answer" by Monday on whether they will fully accept his peace roadmap, which envisages holding elections on November 14.

"Terrorists and people who live abroad want to disrupt the reconciliation plan," he said on national television.

If opposition demonstrators refuse to end their two-month-old rallies, "we have a back-up plan which will lead to a resolution of the problem," he added.

The government and the "Red Shirt" opposition protesters Saturday reaffirmed their commitment to a reconciliation process aimed at ending civil violence that has left 29 people dead and about 1,000 injured.

The latest casualties were two police officers who were killed in gun and grenade attacks close to the Red Shirts' massive rally site, which has shut down most of Bangkok's main shopping district. Nobody claimed responsibility.

The Reds, who blamed the latest killings on elements intent on sabotaging the peace process, said they needed one or two more days to come up with an answer to Abhisit's offer.

"We are not trying to cause a delay but when we are talking about the nation's future we have to consider carefully," Reds leader Nattawut Saikuar told a news conference.

"Dissolving the house and ending the rally are easy. The difficult thing is how to lead the country peacefully to an election, without any political upsets that will destroy the country's democratic system again," he said.

The Reds have signed up to the peace process but are demanding a firm date for the dissolution of the lower house of parliament before dismantling their barricades made from piles of fuel-soaked tyres, bamboo poles and razor wire.

Renegade major general

The United States called for a peaceful resolution to the crisis, which sparked the country's deadliest civil unrest in almost two decades last month, despite a state of emergency in the capital and surrounding areas.

"We call on both sides to urge restraint," Kurt Campbell, the assistant secretary for East Asian and Pacific Affairs, told reporters in Bangkok.

Abhisit said the latest deaths were caused by "terrorists" seeking to disrupt the peace efforts.

He named a renegade major general, Khattiya Sawasdiphol, a Red Shirt supporter also known as Seh Daeng, as an obstacle to an accord, although he did not explicitly accuse him of involvement in the latest bloodshed.

"The person who clearly said he does not want the rally to end is Seh Daeng," Abhisit said, linking him to the Reds' hero, fugitive former premier Thaksin Shinawatra, who was ousted in a 2006 coup.

"He said he will only listen to Thaksin," Abhisit added. "Thaksin is not satisfied with this (reconciliation) plan because there is nothing to solve his personal problems, like his legal cases," Abhisit said.

Thaksin, a telecoms tycoon-turned-politician, now lives in exile to avoid a jail sentence for corruption. In February Thailand's top court stripped him of more than half his 2.3-billion-dollar fortune for abuse of power.

Crowds at the Reds camp have swelled to as many as 100,000 people in the past, but earlier this week when a resolution appeared near, numbers dwindled to just a few thousand as a weary air descended on the rally area.

On Saturday, however, their ranks were boosted by 5,000 more supporters who arrived from the movement's heartland in the rural, impoverished northeast.

The Reds consider Abhisit's administration undemocratic because it came to power in an army-backed 2008 parliamentary vote after a controversial court ruling ousted Thaksin's elected allies.