NEW DELHI: Describing India's strategic engagement with the US as a "national tragedy", Left parties warned the government of "serious consequences" if the civil nuclear deal is operationalized and insisted on considering the "sense" of Parliament on the matter.

Preparing to rake up the issue in Parliament next week, the Left parties asked the government to read its "message" but did not spell out the "consequences" that the UPA will have to face.

"The government enjoys the support of the Left. It is a national tragedy that such a government enters into a strategic pact with imperialist America headed by (George W) Bush. We cannot stomach such an agreement," CPI's Gurudas Dasgupta said at a joint press conference of the Left front here.

"The Prime Minister has said that the government will not go back on the deal. We are also saying that we will oppose the agreement inside and outside Parliament tooth and nail," CPI(M) leader Basudev Acharia said after a meeting of Left parties to decide the strategy in Parliament. The Left asked the Congress to understand the "gravity of the situation".

Dasgupta said." This is an untenable situation. The Left cannot close its eyes to such a development." The Left parties, which are supporting the government from outside, have rejected the 123 agreement and demanded a discussion in Parliament but without voting. CPI leader D Raja said if the government "does not concede to concerns expressed by the Left and put on hold the deal, the consequences will be serious."

Asked about the repercussions, Raja said "the Prime Minister knows that, you know and we all know what will be the consequences". Dasgupta said "It is for the government to read the message and not for us to tell it before hand.

We can only tell. If the government does not understand ... We mean what we say". Raja said Parliament "must give its approval. Without Parliament ratification, we do not think the government can carry forward with the deal."

The government must seek the "sense of the House" and if the majority is against the deal, the agreement should not be operationalized, Acharia said. The Left, however, feels that voting would not be necessary to seek the "sense of the House" as it will be clear when "overwhelming majority" opposes the deal during the debate.

Acharia said it was the duty of the government to convince the country that the assurances given by the Prime Minister in Parliament last year have been honored. The Left cannot "stomach" the deal with "imperialist America", Dasgupta said and promised an "eventful" Monsoon session during which the Left parties will also raise a host of issues including price rise, flood situation, police firing in Andhra Pradesh and the agrarian crisis.

The Left will also demand a Constitutional amendment for making it mandatory for the government to get Parliament's ratification before finalizing and signing any international treaty. A private member bill in this regard has already been moved by CPI's C K Chandrappan.