After more than four years of diplomacy, the Obama administration is struggling to contain the nuclear threats posed by North Korea and Iran, a pair of nations already isolated internationally and resistant to the economic incentives offered in return for an end to their programs.

The nuclear ambitions of both countries predate the Obama administration, which has focused its efforts on international diplomacy to prevent Iran from developing a nuclear weapon and to stop North Korea from restarting its once-
dormant nuclear program.

But amid more bellicose threats from North Korea and on the eve of a new round of talks with Iran, neither the administration nor its Asian and European allies appear any closer to resolving either case.

North Korea brought the Obama administration’s difficulties into sharp relief Tuesday by announcing that it would restart a shuttered nuclear reactor at its Yongbyon facility and increase production of nuclear weapons material.

The administration has played down the North’s recent warnings, and U.S. officials suggested that the threat to restart the reactor might be a bluff. Still, the administration made clear that it is alarmed by recent statements from North Korea and its young leader, Kim Jong Un.

During his first major speech as defense secretary, Chuck Hagel addressed the escalating threats coming from North Korea against the United States and its’ allies in the region. (The Washington Post)

“What Kim Jong Un has been choosing to do is provocative, it is dangerous, reckless,” Secretary of State John F. Kerry said after a meeting with South Korea’s visiting foreign minister.

Kerry noted that he will be in Seoul next week and that the new president of South Korea will meet President Obama in Washington in May. Both Kerry and Foreign Minister Yun Byung-se said that diplomacy could still be salvaged but that the onus is on the North.

In the case of Iran, the administration is pursuing an elusive deal to halt that country’s nuclear advances. Diplomats from the United States and five other world powers will meet with Iranian officials in Kazakhstan on Friday for negotiations aimed at persuading Tehran to agree to limits on its nuclear program. A round of talks in February was hailed as “positive” by Iranian officials, but it yielded no concessions by Iran.

Western diplomats involved in preparations for this week’s talks say Iran is expected to make a new offer that would include an agreement to restrict or suspend some of its production of enriched uranium. But they say Iran is likely to insist on immediate relief from economic sanctions, something that the United States and its European allies are not likely to grant.

A former senior administration official said Monday that chances for a deal in the near future remain slim. “I have such low expectations for what’s going to come out of this next round of talks that I think it’s a mistake to try to set the bar,” the former adviser, Gary Samore, told a panel at the Brookings Institution in Washington. “I think that it really is unrealistic to expect that there’ll be some kind of breakthrough in these talks.”

While Iran says its nuclear program is designed to produce electricity, North Korea has conducted three nuclear tests since 2006. The first two tests used fissile material produced by the reactor at Yongbyon, which was shut down in 2007 as part of a diplomatic deal under which heavy fuel oil was sent to the North.

Pyongyang said Tuesday that it wanted to restart the reactor and other nuclear facilities to ease the nation’s “acute shortage of electricity” and to bolster the “nuclear armed force both in quality and quantity.” Experts who have visited the Yongbyon facility say the small reactor is ill-suited for power production and geared to produce weapons-grade plutonium.

Plutonium can be culled from the spent fuel. When the reactor is fully running, it can produce enough plutonium for about one bomb per year, experts say.

Restarting the reactor will take about six months, “unless they have been doing much of the preparatory work quietly,” Siegfried Hecker, a former director of the Los Alamos National Laboratory who has visited the North’s nuclear facilities numerous times, said in an e-mail.

U.N. Secretary General Ban Ki-moon said he was “deeply troubled” by rising tensions on the Korean Peninsula and called for negotiations to calm them. “Nuclear threats are not a game,” he said at a news conference during a visit to Andorra. “Aggressive rhetoric and military posturing only result in counteractions and fuel fear and instability. Things must begin to calm down, as this situation, made worse by the lack of communication, could lead down a path that nobody should want to follow.

In response to the North’s recent threats, the United States has flown its largest and most powerful bombers over the Korean Peninsula and sent two stealth F-22 fighter jets to South Korea as part of a joint military exercise.

The Pentagon has deployed a second guided-missile destroyer to waters near the peninsula, defense officials said Tuesday.

The USS Decatur has joined the USS John McCain in the region, “where they will be poised to respond to any missile threats to our allies or our territory,” George Little, the Pentagon press secretary, told reporters. Both warships are Aegis-class destroyers that are primarily used for ballistic-missile defense missions. He declined to say whether the Pentagon plans to send other warships or military assets to the region.

A former U.S. official who has visited Yongbyon, speaking on the condition of anonymity to be candid, said the North’s apparent decision to restart the reactor and other nuclear facilities is “very dangerous” because they are not monitored by outsiders.

“So what can we do to stop them?” the former official said. “They can get away with murder there, and we’re left on the outside jumping up and down.”

Experts remain uncertain about the material used in the North’s latest underground test, in February. Some U.S. officials suspect that the device used highly enriched uranium, which would indicate that the North has a second path to nuclear bombs. U.S. officials say the North took significant steps to prevent the release of radioactive traces from the blast, which would have been detected by monitoring stations.

Some experts suspect North Korea has enough leftover plutonium to make four to eight bombs the size of those dropped on Hiroshima and Nagasaki during World War II.

Harlan and Yoonjung Seo reported from Seoul. Craig Whitlock, Scott Wilson and Joby Warrick contributed to this report.