WASHINGTON — The United States on Thursday welcomed Myanmar's signing of an agreement with the UN atomic watchdog that will require it to declare any nuclear activities and allow inspections — the latest step by the former pariah nation toward openness. But citing concern about human rights abuses and ties with North Korea, Republican lawmakers said it is premature to deepen US ties with Myanmar's powerful military. The Obama administration has moved rapidly to ease sanctions against Myanmar as it has undertaken democratic reforms after decades of repressive military rule. The engagement policy has been motivated partly by a desire to cut the military ties that the former ruling junta forged with North Korea. On Tuesday, Myanmar took a step long urged by Washington: the signing the International Atomic Energy Agency's Additional Protocol to its existing safeguards agreements. That could help address lingering suspicions that the secretive junta may have pursued a nuclear weapons program. The State Department said Thursday the protocol would help move the country also known as Burma “increasingly in line with international nonproliferation norms and standards.” Independent nonproliferation experts also welcomed the signing as a promising step, but said it could take several years for Myanmar to ratify and bring the agreement into force. Robert Kelley, a former US government nuclear expert, said that under the agreement the onus is on the nation itself to declare any nuclear activities, peaceful or otherwise, which would then be open for inspection. Myanmar's previous agreement with the IAEA required little disclosure, and Myanmar was unresponsive when the Vienna-based agency in late 2010 sought an inspection. Myanmar denies seeking nuclear weapons, and in 2011 declared it had halted long-stalled plans to obtain a research reactor from Russia. About seven years ago, Myanmar reportedly acquired precision machinery from Germany, Switzerland and Singapore that defectors and some analysts concluded were part of a half-baked attempt to make equipment for enriching uranium, although other experts disputed that conclusion. Defectors also reported Myanmar was mining uranium and converting it into oxides and yellowcake. Kelley, who has researched Myanmar's alleged nuclear aspirations, said he believed the junta unsuccessfully pursued a nuclear program. He said he never found any evidence of nuclear links with North Korea. US officials have been more concerned about Myanmar's purchases from North Korea of missiles and other military equipment. Conventional weapons are beyond the remit of the newly signed agreement, although such trade with North Korea is prohibited under UN Security Council resolutions. At a congressional hearing on Myanmar, Republican lawmakers accused the Obama administration of moving too fast in seeking military cooperation. Defense Secretary Chuck Hagel briefly met his Myanmar counterpart last month, but active cooperation between the militaries has gone little beyond discussions on rule of law and human rights. Still, Rep. Steve Chabot, the republican chairman of a House panel that oversees foreign policy toward East Asia, said the administration has turned a blind eye to congressional concerns. Another Republican, Rep. George Holding, said, “Before we move any closer in military-to-military cooperation, we need to ensure that the Burmese military does not have excessive ties with China and North Korea or (that) those ties are severed.” Rep. Dana Rohrabacher, a Republican, accused Myanmar's military of launching air strikes on ethnic minority groups, which he said was evidence that despite reforms, “the repression of peoples in Burma continues.” — AP