They quoted Dr Singh’s media adviser travelling with him in Nigeria that the prime minister came out with the ‘explanation’ when Mr. Bush called him up in Abuja.

The Left parties, whose support shores up the United Progressive Alliance government, on Tuesday hailed Dr Singh’s ‘communication’ to the US President and hoped the message would be conveyed officially at the UPA-Left panel’s October 22 meeting.

Describing the prime minister’s conversation with Mr Bush as a “positive development”, the leaders of the Left Front told United News of India the government should inform the nation about it and come clean on the deal that led to a major standoff.

The government has yet to convey officially to the Left parties its decision to put the deal on hold.

Meanwhile, India’s Ambassador to the US Ronen Sen will be summoned by the Privileges Committees of the Rajya Sabha and the Lok Sabha for his controversial remark in which he had described the MPs opposed to the deal as ‘headless chicken’.

The Left parties had strongly urged the government not to operationalise the deal that involved negotiating a safeguards agreement with the International Atomic Energy Agency.

The Indian embassy in Washington posted a seven-paragraph statement on its website, outlining the conversation between Mr Singh and Mr Bush.

The White House did not announce that the conversation took place until asked about the Indian embassy statement -- and then confirmed it in language almost identical to the Indian press release.

US officials acknowledged deep disappointment over the development and spent the weekend trying to revive the deal.

“We believe that this is an arrangement that is a positive one and a good one for the United States, for India and for the broader efforts of non-proliferation,” State Department spokesman Tom Casey told a briefing in Washington.

“Certainly, there are steps that … the Indian government will need to take and that we’ll need to take on our side as well to complete this,” he said.

Asked if the Singh government caved in to domestic pressures, Mr Casey said: “I’ll let other people do the Indian political analysis for you.”

Mr Casey said the US administration has had “a number of good conversations” with other nations in the 45-nation Nuclear Suppliers Groups and the IAEA to get their endorsement for the deal.

But the formal discussions with the NSG and IAEA will have to wait until India is ready to move ahead with the deal, he added.

The Left and opposition politicians in India are particularly concerned about a clause in the deal that could end America’s nuclear cooperation with India if New Delhi conducts another atomic test.

The Washington Post, however, reported on Tuesday that the main obstacle did not involve the specific terms of the agreement but India’s internal politics, including fears of leftist parties that India is moving too close to the United States.

“Besieged over the past two months by growing opposition to nuclear energy cooperation with the United States, Prime Minister Singh indicated over the weekend that he would rather save his coalition government than the nuclear pact,” the newspaper said.