The Communist Party of India on Wednesday sought an explanation from the government on why it did not sign a nuclear agreement with Russia [Images] for four more nuclear reactors required in Koodankulam in Tamil Nadu.

"The prime minister will have to explain why the government did not sign this agreement during his visit to Russia. Parliament should be informed about this," CPI National Secretary D Raja said.

He was reacting to reports that the Indo-Russian deal was to have been signed during Prime Minister Manmohan Singh's [Images] official visit to Moscow [Images] on Monday but did not materialise due to last minute hitches.

The government has, however, maintained that the stalled agreement for four more Russian nuclear reactors in Koodankulaam was not a setback to relations between the two countries.

New Delhi has maintained that it first wanted to get an across-the-board India-specific IAEA safeguard for all its nuclear plants and the Nuclear Suppliers Group to amend guidelines to facilitate resumption of nuclear trade, failing which, any nuke deal with Russia will remain just a piece of paper.