03/28/2012 01:49 pm ET Updated Mar 28, 2012

Joe Lieberman, John McCain Ask President Obama To Explain Medvedev Open Mic Comments

WASHINGTON -- Hawkish independent Sen. Joe Lieberman added his voice on Wednesday to criticism of President Barack Obama's open mic gaffe promising Russian President Dmitry Medvedev "more flexibility" on missile defense after the election.

"I thought that President Obama's statement to President Medvedev was disconcerting," said Lieberman of Connecticut at a news conference with Sens. John McCain (R-Ariz.) and John Hoeven (R-N.D.).

"We built that missile defense system to protect our allies and us, particularly from Iran, from an intercontinental ballistic missile carrying a weapon of mass destruction," Lieberman said.

"I don't know what the president meant when he said he'd be more flexible," Lieberman said of Obama's open mike remark on Monday. "The president really ought to reassure all of us that he's going to stick with the program that we're on now because that program is, in my opinion, is critically important to the security of the American people for years and years to come."

On Tuesday after joking "first of all, are the mics on?" Obama said that he was not making any promises beyond pointing out that elections at home and in Russia made substantive, difficult talks unlikely until after the political campaigns are wrapped up.

"Arms control is extraordinarily complex, very technical," Obama told reporters. "Frankly, the current environment is not conducive to those kinds of thoughtful consultations. I think the stories you guys have been writing over the last 24 hours is probably pretty good evidence of that. I think we'll do better in 2013."

But McCain, who is serving as a surrogate for GOP White House front-runner Mitt Romney, said it was clear Obama was caving in to Russia and suggested that his comments on Monday were reason to fear a second Obama term.

"He tries to laugh that off, but obviously when you say to the adversary that I'm going to be quote more flexible ... we know what that means," McCain said. "It means he's willing to compromise to Russian demands concerning missile defense in Europe."

The president is playing fast and loose with national security in my view, McCain added. "This should be a lesson to all of us who were worried about a second Obama term as president of the United States."

A spokesman for Obama's campaign did not address McCain's comments directly but pointed to a memo released on Tuesday casting Romney as a foreign policy lightweight. "While Gov. Romney has no shortage of bellicose rhetoric on foreign policy, he has not followed his tough talk with detailed plans to enhance America’s security or strengthen our alliances," the Obama memo stated. "When Gov. Romney wasn’t literally running from reporters’ questions on foreign policy, he has been all over the map on the key foreign policy issues of our time."

Hoeven, however, insisted that the issue was Obama's unguarded comment and that Republicans would insist that the president clarify it further.

"I think that he needs to explain to the American people," Hoeven said. "I think that's a question that needs to continue to be asked of the president. 'What exactly did you mean by that statement to Medvedev?' This is something the American people need to know."

McCain cast further suspicion on Obama's motives by suggesting the president does not back the European missile defense system, although the administration has been carrying forward with the project.

"Some years ago then Sen. Obama said that he didn't believe in missile defense, so that adds to the skepticism about what he meant," McCain said.

House Speaker John Boehner (R-Ohio), who had declined to criticize the president for the open mic comments while the commander-in-chief was still abroad, on Wednesday piled on, sending a letter demanding explanations for why Obama would make assurances to Russia, which he described as aiding U.S. enemies.

"It is troubling that you would suggest to Russian leaders that their reckless ambition would be rewarded with greater 'flexibility' on our missile defense program after the upcoming election," Boehner wrote. "That has significant implications for the security of our homeland, sends a terrible signal to our allies around the world, and calls into question the effectiveness of your 'reset' policy with the Russian government."

"Your message also implies you understand such concessions would not be supported by the American people or the Congress," he wrote.

This story has been updated to add details of House Speaker John Boehner's letter.