MOSCOW - Legislators in the lower house of Russia's parliament on Friday debated ratification of a pivotal nuclear arms pact with the United States and considered their response to an accompanying U.S. Senate resolution.

The State Duma is to hold the ratification vote for the New START in the third and last reading on Jan. 25, after which it will go to the upper house for final approval. Prospects for the pact's passage aren't in doubt, but Russian lawmakers want to respond to the Senate resolution with a similar motion.

That resolution said the treaty shouldn't restrict U.S. plans to develop a missile defence system. In response, the Duma draft ratification bill says the treaty can only be fulfilled if emerging missile defences don't erode the Russian nuclear deterrent.

The Russian draft bill also emulated the Senate resolution that mentioned increased funding for the U.S. nuclear arsenal by emphasizing the need to modernize Russia's nuclear forces.

The New START would limit each country to 1,550 strategic warheads, down from the current ceiling of 2,200 and also re-establish a system for monitoring that ended with the expiration of a previous arms control pact.

U.S. President Barack Obama pressed strongly for the pact's approval, and Democrats sought to appease some Republican senators by allowing them to raise their concerns about the treaty in the accompanying resolution that does not directly affect it.

The Russian ratification bill also wouldn't interfere with the deal, which is a centerpiece of Obama's efforts to "reset" ties with Russia under President Dmitry Medvedev.

"The treaty is fully balanced and fully conforms with Russia's national interests," Konstantin Kosachyov, the head of Duma's foreign affairs committee, told the lawmakers. "I have not the slightest doubt that the Russian Federation will treat the agreement with the highest degree of responsibility."

Still, the Russian legislators felt obliged to outline their own interpretation of the treaty's provisions. Russia's Foreign Ministry helped them draft the ratification bill.

"Our parliament must respond to the interpretations that distort the sense of the treaty," Foreign Minister Sergey Lavrov told the Duma on Friday.

Lavrov on Friday also dismissed the Senate call for a quick start of U.S.-Russian talks to cut short-range nuclear weapons, saying that such talks must also include potential weaponization of space and conventional armaments.