"The United States reserves the right to make any adjustment to this policy that may be warranted by the evolution and proliferation of biological weapons," Gates said, adding later that "We also recognize the real world we continue to live in."
Former Bush State Department official Nicholas Burns today applauded the new policy.
"The president is clearly signaling that we are really decades away now from the end of the cold war," Burns told ABC News. "That the real threats are…terrorist groups, and they're the renegade states like Iran and North Korea."
The response from Capitol Hill was mostly mute. The top Republicans on the House Armed Services Committee and the Armed Services Strategic Forces Subcommittee both praised and criticized the plan. Their biggest concern is that the administration has ruled out a nuclear strike against non-nuclear countries who are complying with the NPT.
"By unilaterally taking a nuclear response off the table, we are decreasing our options without getting anything in return and diminishing our ability to defend our nation from attack," Rep. Michael R. Turner, R-Ohio, said in a statement.
The president made it clear at the onset of his administration that he would work to reduce nuclear arsenals around the world.
Finalized after more than 100 interagency meetings, the policy review -- which Clinton said is the first NPR to be made public in its entirety -- states the United States will not develop any new nuclear weapons, contrary to what Gates originally recommended. The United States also will not conduct any new nuclear testing or develop new nuclear weapons.
Chairman of the Joint Chiefs of Staff Adm. Mike Mullen, however, said the United States will continue to modernize its infrastructure and bolster the development of other conventional weapons.
"We are going to want to make sure that we can continue to move towards less emphasis on nuclear weapons," President Obama said in a New York Times interview published today, to "make sure that our conventional weapons capability is an effective deterrent in all but the most extreme circumstances."
Today's announcement comes at the beginning of a week and a half devoted to denuclearization, with the expected signing of the U.S.-Russian arms treaty in Prague Thursday and the multi-nation nuclear security summit next week in Washington, D.C.
Obama is scheduled to sign the nuclear disarmament treaty Thursday with Russian President Medvedev. The new arms-control agreement with Russia replaces the Strategic Arms Reduction Treaty (START) that expired Dec. 5. The Obama administration, including Clinton and Gates, had been intensely working on the negotiations on the new arms-reduction treaty for the past year.
ABC News' Jonathan Karl contributed to this report.