Ahead of yet another Congressional hearing on the landmark Indo-US civil nuclear agreement, an American expert has warned lawmakers that rejecting the deal will come with a price -- the poisoning of bilateral relations.

• Support N-deal 

Stephen Weiss, founder and chairman of Business Executive for National Security, also said that Prime Minister Manmohan Singh's [Images] "fragile" ruling coalition could suffer a "fatal political blow" for aligning India "so closely" with the US and the defeat of the deal would embolden anti-American voices in India to claim "we told you so, never trust the Americans".

"Imperfect though it may be, the nuclear agreement now before the US Congress is like any dowry -- turning it down risks spoiling the larger relationship.

• Indo-US nuke tango 

"Indeed, overlooked in the current debate are the dangerous consequences if Congress rejects the agreement or imposes new conditions that make it a deal-breaker for New Delhi [Images]," Weiss said in a write-up in Washington Times.

"American lawmakers take note: You go to the altar with the dowry you have, not the dowry you might want. Trying to renegotiate this nuclear deal could poison the US-Indian relationship for years to come. And rather than love, only mistrust and missed opportunities will follow," he said.

"Unlike nuptials of the past, when Indian brides and grooms met for the first time at the altar, the United States and India have been getting to know one another since President Clinton's landmark visit in 2000. By then, New Delhi had largely shed its Nehruvian socialist past, and today Washington sees India as the attractive partner," Weiss remarked.