Kyl continues offensive against Obama on missile defense

“The president's reelection prospects could suffer if concessions on these systems were to be openly discussed before the election,” Kyl wrote.

The op-ed is the latest attack from GOP lawmakers on Obama’s remarks to Medvedev — captured by a live microphone while the two leaders were attending a nuclear summit in South Korea.

Republicans have turned the comments into a campaign issue, as the Republican National Committee released a video the same day that accused the president of saying one thing and doing another. GOP frontrunner Mitt Romney echoed the RNC video in his criticism, saying the president should explain what else he plans to be "flexible" on. 

Following the remark, Kyl and a group of 43 Republican lawmakers sent a letter to the president asking him for further explanation. House Speaker John Boehner (R-Ohio) followed that up with a letter of his own a day later asking Obama to explain his “troubling” comments.

Obama said last week that he was not “hiding the ball” about his intentions with Russia, and has said publicly he wants to continue reducing the U.S. nuclear stockpile.

Republicans have accused him of ignoring promises he made to gain enough support in Congress for the New START treaty with Russia, and said that the United States should not decrease its nuclear arsenal any further.

“As the president has noted, any new arms-control treaty would have to be supported by the Senate,” Kyl wrote. “Supporting a robust nuclear deterrent and an effective missile defense is a moral obligation for all those who are entrusted with ensuring our nation's security.”

— This post was updated at 3:40 p.m.