Thailand's government stuck to a plan for a February election on Wednesday despite mounting pressure from protesters who have brought parts of Bangkok to a near-standstill, and said it believed support for the leader of the agitation was waning.

Some hard-line protesters have threatened to blockade the stock exchange and an air traffic control facility if Prime Minister Yingluck Shinawatra does not step down by a deadline media said had been set for 9 pm Beijing time.

The unrest, which flared in early November and escalated this week when demonstrators occupied main intersections of the capital, is the latest chapter in an eight-year conflict.

The country's political fault line pits the Bangkok-based middle class and royalist establishment against the mostly poorer, rural supporters of Yingluck and her brother, Thaksin Shinawatra, a former premier ousted by the military in 2006.

Yingluck invited protest leaders and political parties to discuss a proposal to delay the general election, which she has called for Feb 2, but her opponents snubbed her invitation.

While she did not completely rule out a delay, Yingluck reiterated her concerns that the constitution does not allow a postponement of the February 2 polls.

"If people don't want this government they should go out and vote," she said.

After the meeting, the government said the poll would go ahead as scheduled, and it derided the leader of the protest movement, Suthep Thaugsuban.

"We believe the election will bring the situation back to normal," Deputy Prime Minister Pongthep Thepkanchana told reporters. "We can see that the support of Mr Suthep is declining. When he is doing something against the law, most people do not support that."

Protest leaders say demonstrators will occupy the city's main arteries until an unelected "people's council" replaces Yingluck's administration.

Thaksin's rural and working-class support has ensured he or his allies have won every election since 2001, and Yingluck's Puea Thai Party seems certain to win any vote held under present arrangements.

The protesters want to suspend what they say is a democracy commandeered by the self-exiled billionaire Thaksin, whom they accuse of nepotism and corruption, and eradicate the political influence of his family by altering electoral arrangements.

There were no signs of trouble at the two targets named by hardliners in the protest movement - the stock exchange and the central Bangkok offices of AeroThai, which is in charge of air traffic control communication for planes using Thai air space.

AeroThai said it had back-up operations to ensure no disruption to air travel if its control center was shut down.

"For en-route services, AeroThai has set up a backup center working parallel to our primary system," company president Prajak Sajjasophon told Reuters. "We can assure you services will not be affected if protesters force our headquarters to shut down operations."

Suthep's supporters have blockaded at least seven big Bangkok intersections and are also trying to stop ministries from functioning, forcing many to remain closed, with civil servants working from backup facilities or from home.

The protests could cost the economy as much as $30 million a day, according to a survey by the University of the Thai Chamber of Commerce.