Thailand's public sector unions will begin a nationwide strike on Tuesday unless the government quits, union leaders said on Friday, a move likely to deepen the economic impact of a long-running political crisis.
"If the government remains on November 25, we will strike," Sawit Kaewvan, head of an umbrella group representing 200,000 workers at 43 state enterprises, told reporters, reported Reuters.
In August, a partial strike by the unions in support of a long-running anti-government street movement caused havoc on the roads and railways, delaying shipments of commodities ranging from crude oil to rubber.
Sawit urged union members to join Sunday's anti-government rally in Bangkok, called by the People's Alliance for Democracy (PAD) after a grenade attack killed one of their protesters on Thursday.
The PAD accused the government of having a hand in the firing of the grenade into the prime minister's official compound, which PAD supporters have occupied since August.
Besides the dead man, 23 people were hurt in the blast, the most serious in a series of small attacks against the PAD sit-in in the last few weeks. Prime Minister Somchai Wongsawat has denied any responsibility.
There are fears the PAD will try to blockade parliament on Sunday with thousands of supporters ahead of a special session on Monday relating to next month's regional summit to be hosted by Thailand in the northern city of Chiang Mai.
The last time the PAD employed such a tactic, on Oct 7, two people were killed and hundreds injured in running battles with riot police -- the worst street violence in the Thai capital since the army opened fire on democracy protesters in 1992.
House leaders said they were not prepared to move Monday's session to a new venue, setting up a potentially serious confrontation.
"We are talking about the pride and dignity of parliament and the country," Deputy House Speaker Apiwan Wiriyachai told a Bangkok radio station.
The PAD, a loose coalition of royalist businessmen and academics who accuse the government of being a puppet of ousted leader Thaksin Shinawatra, have managed to muster crowds in the tens of thousands this year.
However, in the last few weeks their numbers at Government House have been dwindling, largely through fatigue and the absence of anything inflammatory from the elected administration, which is operating out of temporary offices at an old airport.
Even if Monday passes off without incident, tensions are likely to remain high, with Thaksin -- now in exile having skipped bail in a corruption case -- set to address a mass rally of supporters around Dec 13.
The army has said repeatedly that another coup would not solve Thailand's fundamental political problems, and analysts say it is unlikely to change that view unless major street violence breaks out.