Trinamool Congress today dealt a severe blow to the UPA by deciding to withdraw its ministers from the Union government and its support but left open the doors for a possible rapprochement in the next three days.

The second biggest constituent of the UPA with 19 members in Lok Sabha sprang a surprise after a meeting of its MPs and top leaders with a caveat that the party could reconsider its stand if the government rolls back its decisions.

She wanted total withdrawal of the decision on FDI, raising the cap on subsidised LPG from six to 12 cylinders and reduction of diesel hike from Rs 5 by Rs 3 or Rs 4 for reconsideration of her decision.

At one point Banerjee mentioned 24 cylinders but it was not clear whether she was making a demand for that number.

"We are withdrawing our support... Our ministers will go to Delhi, meet the Prime Minister and tender their resignations at 3 pm on Friday," TMC chief and West Bengal Chief Minister Mamata Banerjee announced after a three-hour meeting.

If the Trinamool Congress goes ahead with its decision to withdraw support, the UPA will be reduced to 251, 21 short of the majority mark of 272 in the 545-member Lok Sabha. However, with the support of outside allies--Samajwadi Party (22), BSP (21) and some others-- the government is still comfortably placed with the support of over 300 members.

Congress, however, was unfazed as it maintained that Trinamool Congress is "still a valuable ally" and said it will discuss with government the issues raised by Banerjee.

Sources said Congress President Sonia Gandhi is expected to take up the matter with Prime Minister, amid indications that the cap on LPG cylinders could be raised from six to nine per year.

The virtual deadline of three days gives Congress and government some room to work out a compromise, observers felt. For this, the government may have to climb down on its stand of not rolling back its last week's decisions.

Significantly, reacting to the development, SP made it clear that it would not be influenced by Trinamool's decision and would take an "independent" view.

Trinamool has six ministers in the Manmohan Singh government-- one of Cabinet rank and others Ministers of State.

Banerjee ruled out supporting the government from outside saying her decision was "not half-hearted".

While announcing her decision, she attacked the Congress, accusing it of indulging in "blackmail" politics and alleged that the FDI decisions were to "suppress the coalgate issue. They wanted to divert attention from coalgate to FDIgate."

Contending that "somebody will have to bell the cat, somebody", she said, "I waited for three-four days. We thought the government will review (its decisions). We wanted to stay in the government but we were not allowed to stay."

Banerjee said her party would not be responsible if the country was forced to go for a mid-term poll.

"This government can stay for three months or six months, I don't know. But they have lost the credibility. And if they cannot maintain friendship with us, then they cannot maintain friendship with anybody," Banerjee said.

Widening the attack on Congress, she brought in issues like coal block allocation scam, blackmoney and fertiliser price rise.

Accusing the Congress of indulging in "blackmail politics", she said whenever it has trouble with any of its allies, it goes to the other.

"When they have trouble with Mamata, they go to Mayawati, if they have trouble with Mayawati, they go to Mulayam, if there is problem with Nitish (Kumar of JD-U), they go to Lalu... This is blackmailing politics," Banerjee said.

Referring to the FDI decision, she said there are 50 million people in unorganised retail sector. "Where will these people go? There will be disaster. It has not been sustainable even in the West."

While Banerjee was holding meeting with her party leaders, the Prime Minister held confabulations with senior Cabinet colleagues P Chidambaram and Sharad Pawar.

Pawar, the leader of NCP, is understood to have assured the Prime Minister that his party is strongly with the government.

Banerjee, at the end of her 72-hour deadline to the Centre, said it was a unanimous decision.

"We are the second largest party in the UPA, but we were never given minimum respect (by the Congress)."

Dismissing reports that the party was divided in taking the drastic decision, she said "it was a 100 per cent unanimous decision. At this juncture we were not in favour of withdrawing support since we had promised during election to support the government for five years.

"We had repeatedly asked the Congress not to take anti-people decisions, but they have gone ahead with it hurriedly without discussing these at the UPA co-ordination committee meetings. It is totally unacceptable," she said.

Stating that the Central government was not a one-party rule, Banerjee said "the government depends on the support of others. But in Bengal, we have a majority of our own and we are not dependent on others."

Banerjee said in Parliament her party will oppose the government at every opportunity.

She brought in issues like coal block allocation scam, black money and the fertiliser price rise to attack the Congress.

"To suppress the coalgate issue, they introduced FDIgate," she said referring to the decision to introduce FDI in multi-brand retail.

She also said that the Centre was planning to introduce the Pension Bill and claimed "this will spell disaster for the salaried class."

Banerjee said, "it is unfortunate for me to announce this decision, but we gave 72 hour time. We have expected this government will at least take some decision. But they did not. We are not allowed to stay in the government, because if we stay they will not be able to take such decisions.

"Four days back I had sent my message to Soniaji and asked her to see that the alliance did not break up. I had requested her to do something. All right, she has not been able to do so, but my personal relations will continue," she said.

"The government may survive three months or six months by taking support of someone or other at times after our departure. It hardly matters to me. We will vote against the government in Parliament whenever opportunity comes. I am sorry to say that they have lost their credibility. We are not responsible if the country is forced to go for a mid-term poll.

Banerjee said, "We cannot support anti-people decisions... Trinamool Congress is a self-sufficient party. We will go to the people in the country and tell them under what situation we had to take this decision," Banerjee said.