"In their verbal duel with the Prime Minister, the Communists have spoken of serious consequences against operationalising the deal. It's high time they took it to its logical conclusion and withdraw support," senior BJP leader Vijay Kumar Malhotra said.

His comments came after the CPI(M) politburo, in a party resolution, described the deal as "unacceptable" and demanded the government should not proceed further on it by starting negotiations with the UN nuclear watchdog IAEA for safeguards.

"The Left should bite instead of barking," Malhotra, whose party had sought a vote in Parliament on the 123 agreement, said. "Empty rhetorics do not work.

"Former Deputy Prime Minister L K Advani had unsuccessfully sought support from CPI (M) leader Prakash Karat to BJP's call for voting on the nuclear pact.

The RSS too has challenged the Left to pull out support to the UPA over the 123 accord.

"If the Left is serious about opposing the nuclear deal in particular and the US hegemony in general, it has no other option but withdraw support to the UPA government," an editorial in Sangh mouthpiece Organiser said.

It said Prime Minister's challenge to the Communists to pull down his government has made their position untenable.

The Sangh write-up insisted that the deal would impose American supremacy over India.

"There is no way now for the Prime Minister to pretend that the deal is in India's interest. This is a one-way street where only the big bully has all the right of way," it said.

Manmohan Singh's hard talk and the deal, the editorial added, have given the Left a golden opportunity to introspect.