WASHINGTON — Facing concerns from U.S. Republican lawmakers that a new nuclear arms control treaty with Russia could hinder U.S. missile defense activities, a Pentagon official said April 20 that the pact actually permits more freedom of action in this area than before, particularly in testing.

U.S. Army Lt. Gen. Patrick O’Reilly, director of the Missile Defense Agency, told the Senate Armed Services Committee that the New START (Strategic Arms Reduction Treaty) is less constraining than the previous START. Signed in 1991 and ratified the following year, START limits the Missile Defense Agency’s ability to use air- and sea-launched targets, “which are essential for the cost-effective testing of missile defense interceptors against medium- and intermediate-range missile targets in the Pacific area,” O’Reilly said.

START also limits the United States to five facilities for launching missile defense targets, he said. That constraint will be removed once the New START is ratified by the designated legislative bodies in the United States and in Russia, he said.

U.S. President Barack Obama and Russian President Dmitry Medvedev signed the New START April 8 in Prague, Czech Republic. The pact reduces to 1,550 the number of deployed nuclear warheads each country is allowed and permits a lower number of deployed and nondeployed nuclear launchers and heavy bombers.

The United States and Russia appear to have different views on the treaty’s relationship to missile defense. A fact sheet posted on the White House Web site March 26 said “the Treaty does not contain any constraints on testing, development or deployment of current or planned U.S. missile defense programs or current or planned United States long-range conventional strike capabilities.”

However, Russian Foreign Minister Sergei Lavrov told reporters in Moscow April 6 his nation will have the right to pull out of the treaty if U.S. missile defense capabilities threaten the effectiveness of Russian nuclear forces.

Despite assurances from U.S. Secretary of Defense Robert Gates that the treaty will not affect U.S. missile defense plans, Sen. John McCain (R-Ariz.), the committee’s ranking member, remained skeptical.

“I’m concerned the treaty may establish a low threshold for Russia to withdraw, citing future U.S. missile defense deployments as the rationale,” McCain said. “Unilateral Russian statements to this effect are troubling. Missile defense is not and should not be viewed in Moscow as some new form of post-Cold War aggression. It is rather a reasonable and prudent response to the very real threats that the Iranian and North Korean regimes pose to the United States, our friends and our allies.”

James Miller, principal deputy undersecretary of defense for policy, said the administration believes Russia is very unlikely to exit the New START.

Lawmakers also pressed the witnesses on the administration’s September decision to overhaul plans to deploy missile defenses in Europe to protect deployed U.S. forces and allied nations, as well as provide some additional measure of coverage for the U.S. homeland.

The previous administration planned to place a radar site in the Czech Republic and 10 Ground Based Interceptors in Poland. These would have been two-stage versions of the three-stage interceptors now deployed in Alaska and California.

The new plan, called the Phased Adaptive Approach, calls for U.S. Navy ships equipped with Standard Missile-3 interceptors to be deployed in European waters in 2011. Then in 2015, land-based Standard Missile-3 batteries would be placed in Poland and Romania. These missiles would defend all European NATO members from short- and medium-range missiles launched by Iran, O’Reilly said. The United States would also continue to develop a larger version of the missile, dubbed the Block 2B, which could defend the United States from an Iranian ICBM attack by 2020.

Sen. James Inhofe (R-Okla.) cited a recent intelligence estimate that Iran could have ICBM capability as soon as 2015, leaving a gap of about five years when the United States is not protected from Iranian missiles. Under the previous administration’s plan, the two-stage interceptors in Poland would have defended the United States against Iranian ICBMs by 2015, he said.

O’Reilly countered that the previously planned European missile defense site would not have been operational until 2017. He added that the United States is already protected from Iranian ICBMs by the interceptors in Alaska and California.

The territorial U.S. missile shield would have a 92 percent chance of intercepting a missile launched from Iran, and that likelihood would only have been increased by 3 to 4 percentage points under the previous European missile defense plan, Marine Corps Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff, told Congress last year. Though the Pentagon does not plan to deploy the two-stage variant of its Ground Based Interceptor, it will continue to develop and test the missile as a hedge against a threat that arises more quickly than anticipated or unexpected development problems with the larger Standard Missile-3. The first test of the two-stage interceptor is slated for June, he said.

Sen. Joseph Lieberman (I-Conn.) also expressed concern over coverage against Iranian ICBMs and questioned the Pentagon’s rationale for planning only two test flights of the two-stage Ground Based Interceptor between now and 2016.

O’Reilly said the two-stage interceptor is nearly identical to the three-stage variant.