This photo provided by the North Korean government shows a test of military weapon systems in North Korea.

In this May 20, 1998, file photo former prime minister Atal Bihari Vajpayee visits the nuclear test site in Pokhran.

In this May 11, 1998, file photo former prime minister Atal Bihari Vajpayee announces India's nuclear test, in New Delhi. .

In this photo, command post facilities of North Korea's nuclear test site are blown up in Punggye-ri, North Korea.

Smoke and debris go up in the air as the entrance to the north tunnel at North Korea's nuclear test site is blown up during a media tour of dismantling the test site at Punggye-ri,...

In this photo, facilities of North Korea's nuclear test site are blown up in Punggye-ri, North Korea.

Iranian demonstrators burn a picture of the U.S. President Donald Trump during a protest in front of the former U.S. Embassy in response to President Donald Trump's decision to pul...

Iranian demonstrators burn representations of the U.S. flag during a protest in front of the former U.S. Embassy in response to President Donald Trump's decision to pull out of the...

Protesters march during an anti-nuclear demonstration in Taipei, Taiwan. Hundreds of Taiwanese took to the streets and demanded the government to scrap its nuclear energy usage.

Foreign Secretary S Jaishankar shakes hands with Deputy Head Nuclear Affairs, Security Policy Department (Netherlands), Janneke Vrijiland (L) as Chief Councellor, Ministry of Forei...

Prime Minister Narendra Modi, left, and Japan's Prime Minister Shinzo Abe shake hands after signing a joint statement at Abe's official residence, in Tokyo, Japan. After their bila...

Phon van den Biesen, lawyer for the Marshall Islands, left, shake hands with India's Ambassador J.S. Mukul, right, prior to the start of the World Court session in The Hague, Nethe...

Xi Jinping, Obama and Modi at the Nuclear Security Summit

A South Korean man watches a TV news program showing an image published in North Korea's Rodong Sinmun newspaper of North Korean leader Kim Jong Un at Seoul Railway station in Seou...

Prime Minister Narendra Modi shakes hands with Prime Minister of United Kingdom (UK) David Cameron during a bilateral meeting at the Nuclear Security Summit in Washington.

Prime Minister Narendra Modi arrives for a bilateral meeting with Canadian Prime Minister Justin Trudeau (not pictured) at the Nuclear Security Summit in Washington.

Canadian Prime Minister Justin Trudeau takes part in a bilateral meeting with the Prime Minister Narendra Modi at the Nuclear Security Summit in Washington.

U.S. Secretary of State John Kerry talks with Iranian Foreign Minister Mohammad Javad Zarif, right, after the International Atomic Energy Agency (IAEA) verified that Iran has met a...

Iranian President Hassan Rouhani, right, welcomes U.N. nuclear chief Yukiya Amano for their meeting in Tehran, Iran.