Russia has warned US lawmakers that any change to the new nuclear arms disarmament treaty between the two countries could destroy the pact¹.

俄罗斯警告美国立法者，对双方签署的新核武器裁减条约进行的任何改变即有可能破坏该条约。

Foreign Minister Sergei Lavrov said the New Start treaty "cannot be reopened, becoming the subject of new negotiations²" according to remarks reported by Interfax news agency.

Republicans in the US Senate have recently pushed to change its wording（措辞，用语） .

Two-thirds of the 100 US senators must back the treaty for it to be ratified³（批准） .

"The Start agreement, which was drafted on the basis of strict parity⁴, completely meets the national interests of both Russia and the United States," Mr Lavrov told Interfax.

"It cannot be reopened, becoming the subject of new negotiations," he added.

In Washington DC, top Republican senators have pledged to oppose the treaty, with some objecting to the tight time frame before the new Congress begins in January and others saying they fear it will prevent the US from developing a missile defence system.

But White House spokesman Robert Gibbs said on Monday he believed the treaty had the 67 votes required for passage.

Adm Mike Mullen, chairman of the US Joint⁵ Chiefs of Staff, sent a letter to congressional leaders on Monday urging them quickly to ratify⁶ the agreement.

"This treaty enhances our ability to do that which we in the military have been charged to do: Protect and defend the citizens of the United States," he wrote.

"I am confident in its success as I am in its safeguards. The sooner it is ratified, the better."

Security imperative⁷

Republican Senator Jon Kyl from Arizona argued on Sunday that the "treaty needs to be fixed⁸", and that not enough time had been allowed for senators to consider it.

Senate Minority Leader Mitch McConnell from Kentucky said he would oppose the accord in a vote expected on Tuesday, further complicating⁹ the prospects¹⁰ for President Barack Obama in resolving one of the largest issues on his foreign policy agenda.

But Senate Democrats¹¹ said on Sunday they expected ultimately to have enough votes to ratify the treaty - which would trim（修剪，整理） US and Russian arsenals¹²（军械库） to 1,550 deployed¹³ nuclear warheads - a cut of about 30% from a limit set eight years ago.

Mr Obama wants the Senate to vote on the issue before January when Republicans will increase their numbers in the Senate by five, dimming the prospects for the accord.

The president, who has said the pact would make the world safer, lobbied senators by telephone on Monday to pass the accord, calling the treaty a national security imperative, said deputy press secretary Bill Burton.

In his weekly address to the nation on Saturday, Mr Obama said the "safety and security of America" was at stake.

The treaty would limit the number of deployed ballistic missiles（弹道导弹） or nuclear bombers¹⁴ to 700 as well as establish a new mechanism¹⁵ for sending inspectors¹⁶ to the other country's nuclear sites.

Since the previous Start treaty expired in December 2009, Russia and the US have not been able to conduct inspections¹⁷ of each other's nuclear stockpiles（库存，储备） - leading to uncertainty¹⁸ about what the other side is doing.