[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2010/images/03/22/art.romney.0321.gi.jpg caption ="Romney is getting tough on President Obama's foreign policy moves."](CNN) – Calling the arms reduction treaty with Russia signed earlier this year President Barack Obama's "worst foreign policy mistake yet," former Massachusetts Gov. Mitt Romney is urging senators not to ratify the agreement.
In a strongly-worded op-ed in the Washington Post Tuesday, the onetime and potential future Republican White House candidate says the agreement – signed last April – dangerously impedes the United State's ability to protect itself form potential nuclear proliferating states such as Iran and North Korea.
"By all indications, the Obama administration has been badly out-negotiated," Romney writes. "Perhaps the president's eagerness for global disarmament led his team to accede to Russia's demands, or perhaps it led to a document that was less than carefully drafted."
"Whatever the reason for the treaty's failings, it must not be ratified: The security of the United States is at stake," he adds.
The new Strategic Arms Reduction Treaty - known by its acronym, START– builds on a previous agreement that expired last December. It cuts the number of nuclear weapons held by the United States and Russia by about a third.
"It significantly reduces missiles and launchers," Obama said in April of the new treaty, which lasts for 10 years. "It puts in place a strong and effective verification regime. And it maintains the flexibility that we need to protect and advance our national security, and to guarantee our unwavering commitment to the security of our allies."
It remains unclear when the Senate will vote on ratification, but more than 30 national security figures from multiple administrations and both parties expressed their support of the treaty late last month.
But the treaty's detractors, including Romney, say the proposal forces the United States to seek Russian approval with respect to its own nuclear defense decisions.
"America must effectively get Russia's permission for any missile defense expansion," writes the former Massachusetts governor. "Moscow's vehemence over our modest plans in Eastern Europe demonstrate that such permission would be extremely unlikely.
Romney's foray into a hot-button international issue is another sign the former presidential candidate is gearing up to challenge Obama in 2012 and seeking to expand his foreign policy portfolio. While the Massachusetts Republican and former businessman has been a constant critic of Obama's economic policies over the past two years, his commentary on international issues has been noticeably less pronounced.