Senior Communist Party of India-Marxist leaders, including general secretary Prakash Karat, on Saturday met Prime Minister Manmohan Singh [Images] and Congress chief Sonia Gandhi [Images] amid an assertion by Left parties that the onus of resolving the standoff over the Indo-US nuclear deal lies with the government.

Karat and politburo member Sitaram Yechury were closeted with Dr Singh and Sonia Gandhi for about an hour.

External Affairs Minister Pranab Mukherjee, who is working on reconciliation efforts with the Left, was also present during the deliberations.

Karat and Yechury did not speak to the waiting mediapersons, but sources said the onus of resolving the standoff lay with the government.

The CPI-M has also convened an emergency meeting of its central committee next week to discuss the party's future stand on the nuclear issue.

After Karat and Yechury left the prime minister's residence, Dr Singh, Gandhi and Mukherjee held their own consultation over the matter.

The Left leaders have apparently conveyed that their parties are not willing to go back on their stand on the Indo-US nuclear deal.

Left leaders have made it known that the minimum they expected from the government was that the civil nuclear deal, which has been outrightly rejected by them earlier is not operationalised.

Karat and Yechury met Dr Singh at the end of the party's two-day politburo meeting, which deliberated on its strategy in dealing with the stand-off with the government over the contentious deal.

In the midst of the politburo meeting, CPI-M leaders have already held consultations with other Left parties apparently to convey their united opposition to the deal during the meeting with the prime minister.

The meeting with the prime minister also comes ahead of a press conference by Karat on Saturday evening where he is expected to announce the party's strategy in the wake of the government's decision to go ahead with the deal.

The CPI-M was of the view that the government has deviated from the Common Minimum Programme commitments of pursuing an independent foreign policy and is sharply critical of the Congress-led coalition for entering into a strategic partnership with "imperialist" America.

Other Left parties are more strident in their demand for reviewing support to the government with CPI general secretary A B Bardhan saying that it has become "untenable" and the Left should extend "merit-based" support now.

Bardhan feels that the UPA-Left Coordination Committee, the mechanism so far being used for consultations on key issues, has become "dead" and there is no point in carrying forward with it.

Revolutionary Socialist Party leader Abani Roy said it is "high-time" that the Left review its support to the government otherwise it will become a "laughing stock" among the people.

"Something should be done. Either pull out from the UPA-Left Coordination Committee or make the support issue-based," said Roy, whose party is a minor constituent of the Left bloc having three MPs in Lok Sabha.

Forward Bloc general secretary Debabrata Biswas met CPI-M leaders on Saturday morning and conveyed to them his party's stand on the deal and support to any move that puts operationalising of the 123 agreement on hold.

"If is crystal clear that after the 123 agreement was signed there has been a visible tilt in our foreign policy practises towards the US," he told PTI referring to India's participation in the joint naval exercises with the American Navy and the vote on Iran.

Since the days of Jawaharlal Nehru till A B Vajpayee, Indian political parties have generally been unanimous on the foreign policy issues, he said adding, that even during Indira Gandhi's [Images] emergency period her foreign policy was not questioned "which is happening now."

The meeting with prime minister comes after a dinner West Bengal Chief Minister Buddadeb Bhattacharya had with him last night and telephonic talk between Yechury and Pranab Mukherjee, initiatives seen as efforts to defuse the crisis.

Bhattacharya also briefed the politburo meeting about his discussions with the prime minister.