Washington's commitment to defending Europe from missile attacks remains unbending, a top US security official said Wednesday, after it froze the final phase of a plan to counter threats from North Korea and Iran.
"Let me emphasise the strong and continued commitment of the United States to NATO missile defence. That commitment remains ironclad," said Rose Gottemoeller, acting under secretary of state for arms control and international security.
Speaking at the Geneva Centre for Security Policy, an international think-tank, she rejected claims that Washington was watering down its European anti-missile moves.
US President Barack Obama's current plan -- adapted from one drawn up under his predecessor George W. Bush -- envisages a defence shield comprising a super-powerful radar in Turkey, SM-3 IIA interceptors aboard frigates in the Mediterranean and 48 interceptors split between Poland and Romania.
But last Friday, US Defence Secretary Chuck Hagel said Washington would deploy 14 anti-missile interceptors in Alaska, up from the current 30, in response to mounting concerns about nuclear-armed North Korea.
That meant calling off the fourth and final phase of the European plan, which foresaw upgraded SM-3 IIB "missile-killing" technology being deployed within a decade.
Besides Alaska, Washington is eyeing sites on the US east coast, and plans a new radar facility with Japan, Gottemoeller said.
"These combined steps serve to strengthen missile defences for the protection of the US homeland and our allies," she said.
"Phase one through phase three of the European phased adaptive approach, including sites in Romania and Poland, will provide coverage of all European NATO territory as planned by 2018."
The US shield is linked to a plan for Europe which NATO launched last May. Both have raised hackles in Russia, which dubs them a threat on its doorstep.
Gottemoeller, a fluent Russian speaker involved in arms control issues since the early 1990s, questioned Moscow's stance.
"The United States' missile defence programmes are very limited in nature. They focus on regional threats from Iran and North Korea," she said.
Since the Cold War era of the 1980s, Moscow has made "incredible progress" on counter-measures for missile defence systems, she said.
"Therefore, I see no objective reason to say that very limited American missile defence capabilities are any threat to Russia's nuclear deterrent at all.
"We believe that cooperating on these missile defence developments is the best way to build mutual confidence."