US Defence Secretary Ash Carter has said that India has generally been responsible with its nuclear technology, while Pakistan's history of nuclear weapons has been "entangled in tensions". Speaking at an air force base in North Dakota, Carter said: "The landscape of nuclear weapons has changed in the last 25 years."
He said while the US has not contributed much to improve its nuclear resources, other countries have been proactive in boosting the number of weapons and delivery options.
"We didn't build anything new for the last 25 years, but others did, including Russia, North Korea, China, India, Pakistan and for a period of time, Iran while our allies around the world, in Asia, the Middle East, and Nato, did not," the Press Trust of India quoted Carter as saying.
He praised India for "showing responsible behaviour" with its nuclear technology.
India has been trying to enter the elite 48-member Nuclear Suppliers' Group (NSG). Washington, along with several other countries, have been backing Delhi's bid but China has remained a stumbling block.
Referring to Pakistan, which is also seeking NSG membership, the defence secretary said: "Pakistan nuclear weapons are entangled in a history of tension, and while they are not a threat to the United States directly, we work with Pakistan to ensure stability."
As for China, which backs Pakistan for the NSG but not India, Carter said, Beijing is also conducting itself professionally in the nuclear arena, "despite growing its arsenal in both quality and quantity".
He, however, expressed concerns over North Korea's nuclear programme. The isolated country has come in for heavy criticism from all sides after its latest and the biggest nuclear test on 9 September. Pyongyang's nuclear technology has always been seen as a threat to the US and South Korea's national security.
"It is essential that the US maintains its nuclear deterrence. America's nuclear deterrence is the bedrock of our security and the highest priority mission of the department of defence," he said.
According to him, deterrence should be credible and must extend to all its allies – Japan and South Korea - in the region to "ensure we're poised to address nuclear deterrence challenges in Asia".
He raised doubts about Russian leaders' strategies, and said Moscow has "modernised its nuclear arsenal".
Carter attacked both North Korea and Russia citing the two countries as an example of the "unwise" that would carry out smaller but "unprecedentedly terrible attacks". He also accused the two neighbours of trying to "coerce a conventionally superior opponent to back off or abandon an ally during a crisis".
"We cannot allow that to happen, which is why we're working with our allies in both regions to innovate and operate in new ways that sustain deterrence and continue to preserve strategic stability."