United Nations — Nuclear weapons are easier to get than ever before, and that means new risks as more countries seek to develop their programs.

"In general terms, the technology to develop nuclear weapons is an old one, dating back 70 years, and after that lots of progress has been made in technology," said Yukiya Amano, Director General of the International Atomic Energy Agency (IAEA). "You can get the information, you can get the material, the education. It's available."

The nuclear weapons club has remained small; only a handful of countries have fully developed programs. But Amano, the world's so-called nuke chief, warns that "the current environment" makes it "easier for countries to proliferate."

International Atomic Energy Agency (IAEA) chief Yukiya Amano poses ahead of a meeting of IAEA Board of Governors, Nov. 22, 2018, at the agency's headquarters in Vienna, Austria. Getty

"That is one of the reasons why we have to strengthen our activities to prevent the proliferation of nuclear weapons and verify that all the material and equipment stay for a peaceful purpose," he said.

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The IAEA was formed in 1957 and is charged with promoting the safe, secure and peaceful use of nuclear technology -- and preventing the proliferation of nuclear weapons. Amano, a Japanese diplomat who became head of the nuclear watchdog agency in 2009, sounded one reassuring note in a wide-ranging interview with CBS News: The threat "does not keep me up at night… the IAEA is doing its job."

Here's how Amano sees the state of nuclear technology in three key countries: North Korea, Iran and Saudi Arabia.

North Korea's nuclear program advancing

Amano said that over the last decade North Korea's "nuclear program has significantly expanded."

"Over the past year, activities at some facilities continued or developed further," he said.

His comments come after warnings from South Korean officials and independent analysts that, with U.S. efforts to negotiate the "complete denuclearization" of the Kim regime stalled, North Korea has rebuilt its primary long-range rocket test site and is also operating its main nuclear research facility.

The North has explicitly warned that it could resume nuclear and long-range missile tests.

Amano said the IAEA "is the only international organization that can verify and monitor denuclearization in an impartial, independent and objective manner," but with the U.S. talks -- the only real current dialogue with North Korea — going nowhere, there was little hope that inspectors could enter the isolated country any time soon.

Ever hopeful, Amano noted that the IAEA was ready and able to send a team of inspectors into the country "within weeks," if an agreement were to be reached.

Iran still sticking to nuke deal

"I don't see activities that are contrary to the Iran nuclear agreement ... but we need to monitor very, very carefully," Amano said of the international agreement that the Trump administration unilaterally walked away from last year.

All of the other parties to the agreement hammered out by former President Barack Obama; Iran, Russia, China, France, Germany, Britain and the European Union, are still trying to keep it viable.

Under the 2015 deal, Iran agreed to limit its nuclear program in exchange for sanctions relief. The IAEA has said consistently since the agreement was reached that Iran continues to abide by it, and he confirmed on Tuesday to CBS News that the agency's "inspectors have had access to all the sites and locations in Iran which they needed to visit."

Mr. Trump had long bashed the deal as too generous to Tehran. He pulled the U.S. out for that reason — the White House has never claimed that Tehran was in violation of the deal.

"So far they are implementing" the agreement, Amano said of Iran. He noted that the U.S. is "a very important country, so, of course, it (the U.S. withdrawal) has impact."

Saudi Arabia's nuclear energy bid

Saudi Arabia is eager to join the nuclear energy community, as rapid economic development has left it hungry for electricity. The kingdom is currently reviewing bids from international companies to build its two first nuclear reactors, but it is not currently held to the most rigid international standards for nuclear oversight. That, experts and the IAEA say, is a problem.

The Trump administration has appeared keen, regardless, to push ahead and secure the contract to help build a Saudi nuclear energy program for a U.S. firm. The White House has said if the U.S. doesn't get the contract, a country with less interest in ensuring a verifiably safe and legal nuclear program may get it instead.

Westinghouse is leading a U.S. consortium competing for the contract against companies from China, France, Russia and South Korea.

In the late 90s the IAEA adopted a new, stricter monitoring program known as the "additional protocol." Many countries with nuclear programs, old and new, have agreed to adhere to the new oversight mechanism, but not Saudi Arabia.

Amano said the additional protocol is, "a powerful verification tool that gives the Agency broader access to information about all parts of a State's nuclear fuel cycle. It also gives our inspectors greater access to sites and locations, in some cases with as little as two hours' notice."

Saudi Arabia insists it is only pursuing nuclear energy, not weapons, but remarks by the conservative Islamic kingdom's future king have led to concerns that it could change its mind on that point.

Last year Saudi Crown Prince Mohammed bin Salman told "60 Minutes" that his country "does not want to acquire any nuclear bomb — but without a doubt, if Iran developed a nuclear bomb, we will follow suit as soon as possible."

"I think there is indeed a danger of a slippery slope," Gary Sick, senior research scholar at Columbia University's Middle East Institute and a professor at the School of International and Public Affairs, told CBS News. He believes Saudi Arabia should be held to the same strict standard Iran has been.

The world "should insist on the same level of assurance; (that) under no circumstances will it ever seek, develop or acquire any nuclear weapons," Sick told CBS News.

Brett Bruen, the former Global Engagement Director at the White House, told CBS News that Saudi Arabia "is precisely the sort of country that shouldn't have access to our nuclear technology. Even if we see the need for an alliance of convenience against Iran and ISIS, that doesn't necessitate that we hand over the recipe for our secret sauce."

The IAEA has been working with Saudi Arabia for several years, and even the soft-spoken Amano wants additional verification for the kingdom.

"Not only Saudi Arabia, but I am asking all the countries to implement the additional protocol. This would increase confidence," Amano said.