The Bengal alliance came under strain today as the Congress leaned towards the Left in Punjab and Mamata Banerjee dubbed her ally 'a burden rather than an asset'. Provoked by the Congress' Punjab plan ahead of elections there and Bengal party leader Somen Mitra's recent barbs, Mamata said she had neither closed her option to return to the NDA nor given up plans to go it alone in future. 'We cannot support any kind of entente with the CPM or other Left parties in any state. We cannot maintain our alliance with the Congress, if it decides to fight the elections with the CPM's help. If the alliance is broken, we should not be held responsible,' she said. Buckling under a similar threat two months ago, the Congress had overruled then Assam party chief Tarun Gogoi's suggestion of a deal with the Left. But today, the Congress looked unfazed. General secretary Motilal Vora said in New Delhi: 'The Punjab party chief has been authorised to hold talks with the Left parties. We have no qualms about a tie-up.' This added fuel to the spark lit by Mitra last Sunday, when he said the 'Bangla Bachao Front' led by Mamata, of which his party was a component during the election, had disintegrated for all practical purposes. In response, Mamata said: 'If the alliance collapses, the state Congress will be solely responsible. It will not pose any problem for us. We will go alone and continue our fight against the CPM.' Mamata, however, made it clear that she would not take the initiative to snap the ties. 'If the state Congress leaders do not feel the need for going along with us now, we will find our own way,' she asserted. The sentiments were reciprocated in the Congress headquarters. Most of the Congress Working Committee members said they were 'psychologically' prepared to part ways. 'We had made it clear before and we are saying it now - the Congress would not take the lead in snapping ties. However, if she wants to pull out, we cannot help it,' a party leader said. Party sources said Congress chief Sonia Gandhi, now in the US, has adopted a 'neutral stand'. Mamata hinted that she was not in a hurry to re-enter the NDA. 'We will consult every MP, MLA and party leader before taking a decision, which will be a collective one,' she said. But eyebrows were raised when Mayor and Trinamul legislator Subrata Mukherjee demanded in the Assembly a censure motion against the Prime Minister for acknowledging in haste Pervez Musharraf's presidential status.