Colombia's government and FARC rebels will sign a controversial revised peace accord Thursday to end their half-century conflict, set to be ratified despite bitter complaints from opponents.

Under pressure for fear that a fragile ceasefire could break down, the government and the Revolutionary Armed Forces of Colombia (FARC) said they will sign the new deal at 1630 GMT and immediately take it to Congress.

The plan bypasses a vote by the Colombian people after they unexpectedly rejected the first version of the deal in a referendum last month.

The accord aims to end Latin America's last major armed conflict. But opponents say it is too soft on the leftist FARC force, blamed for many thousands of killings and kidnappings.

The document is expected to pass after being debated next week. President Juan Manuel Santos and his allies hold a majority in the legislature.

Santos, who has staked his presidency on ending the conflict, won this year's Nobel Peace Prize for his efforts -- giving him a boost just five days after the shock referendum defeat.

A recent wave of alleged assassinations in conflict areas has raised pressure to seal a deal fast.

"There is no time to waste," Santos said.

"Lives have been lost and many more are in danger."

But an aftermath of discord and uncertainty appears likely as opponents promised to keep resisting.

"We invite citizens to persist in the struggle for the future of democracy," said the Democratic Center Party led by conservative ex-president Alvaro Uribe.

"In the coming days, we will examine various actions to call the people into the streets and democratic spaces," it added in a statement.

- Opposition objections -

Thursday's signing will be low-key compared to that of the original deal in September. Then, Santos and FARC leader Rodrigo "Timochenko" Londono held a triumphant ceremony with 2,500 guests including 15 heads of state.

The new ceremony will be held in the Colon Theater in Bogota -- relatively small, with a capacity of just 800.

"With today's signing, the hope of peace is coming alive," tweeted the FARC's chief peace negotiator, Ivan Marquez.

"It will be a project of self-construction in which all of us must work."

Government and FARC negotiators presented a redrafted version of the deal earlier this month.

But Uribe complained it still did not satisfy his key demands, notably on punishing FARC leaders for their crimes.

Under the deal, the FARC would disarm and become a political party.

Uribe and his allies say rebel leaders guilty of war crimes should not be allowed to run for office.

They also want guarantees for state police and soldiers who may face trial over their actions in the conflict.

A survey by pollster Datexco published on Wednesday found that 58 percent of people want more revisions to the deal, in line with opposition demands.

- Bypassing voters -

Congress will open a debate on the deal from next Tuesday.

But Uribe's party has demanded a second referendum, accusing Santos of using Congress to impose the agreement on the people.

On the streets of Bogota, Angie Suarez, 21, a sales assistant, said it was not fair to push the deal through Congress.

"They go over our heads, as if our opinion meant nothing," she said.

But street vendor Manuel Duran, 40, thought it was "better for Congress to do it" because another referendum would "divide the country."

- Fragile ceasefire -

A two-way ceasefire between the government and FARC has been in force since August, but both sides have warned it is fragile.

Santos met with top officials on Tuesday to discuss a recent wave of alleged political killings in southern conflict zones.

Separately, two FARC guerrillas were killed last week in what the authorities said was a clash with the army.

The Colombian conflict has killed at least 260,000 people and displaced seven million since it erupted in 1964, according to the authorities.