But Prime Minister Abhisit Vejjajiva did not say when security forces planned to regain control of the Red Shirts' vast protest site, which has been fortified with barricades made from truck tires and sharpened bamboo poles.

The Reds, who are demanding elections to replace the government, have occupied the Ratchaprasong intersection for three weeks and fear a crackdown is looming after Abhisit rejected their offer of a compromise.

"There will be a retaking of Ratchaprasong but the process, the measures, how and when it will be done we cannot disclose because it depends on several things," said Abhisit.

"The main point now is not whether or not to disperse but how to solve the whole problem," added the premier, who has been holed up in a military barracks since street rallies erupted in mid-March.

The pre-recorded televised appearance by the premier and army chief General Anupong Paojinda was seen as an attempt to quash speculation of a rift between the two men on how to deal with the crippling political crisis.

The stalemate rekindled fears of more unrest and a heavier toll on Southeast Asia's second-biggest economy as more retailers shut their doors and tourist numbers dwindle.

Police reinforcements are being brought into the capital to forcibly disperse thousands of protesters occupying some central areas, said red shirt leader Jatuporn Prompang.

"We will try to block every spot we can in a bid to stop killing. We don't want to see anybody die," he said.

The army's failed attempt to eject red shirts from another site in Bangkok on April 10 led to clashes that killed 25 and wounded more than 800.

Coming after red shirts stopped a troop train in the north last week, the blockade raises questions over whether Abhisit can exert full control over rebellious parts of Thailand as the deadly protests enter a seventh week.

Anupong said the military -- which mounted a 2006 coup that forced then-premier Thaksin Shinawatra out of power - would follow government orders.

"We are an army for the nation, for the monarchy and for the people. We will do our job without taking sides," he said.