The world is “closer than ever” to reaching a nuclear deal with Iran, US Secretary of State John Kerry proudly announced on Monday.

Speaking at an international gathering to discuss nuclear disarmament at the United Nations, the secretary made clear that while there is hope for the future, the struggle is far from over as many key issues remain unsolved.

“I know as well as anyone that we have a long way to go,” he stated, referring to a nuclear-free world. “We know that we can cut back ever further.”

The conference is tasked with reviewing the Nuclear Nonproliferation Treaty (NPT) and setting guidelines seeking the elimination of some 16,000 nuclear weapons around the world. Israel attended the conference as an observer for the first time in over two decades.

Major concerns for conference attendees include the lack of disarmament progress by the US and Russia, who hold more than 90 percent of the world’s nuclear weapons. Civil society groups criticized the US and Russia for spending billions of dollars in modernizing their nuclear arsenals.

According to the US, the government is “maintaining and servicing” its nuclear weapons and not bolstering its arsenal.

In his speech, Kerry singled out North Korea as “the most glaring example” of a country ignoring its global obligation towards disarmament. The secretary said the US will open talks with Pyongyang but only if it shows “it’s serious.”

On the sidelines, Kerry met with Iran’s Foreign Minister Mohammad Javad Zarif as talks continue between the P5+1 and the Islamic Republic.

With a June 30 deadline, diplomats hope to reach a final deal with Iran, including the questions of when to lift global sanctions imposed on the country and the military aspect of Iran’s nuclear program.

Zarif, who is expected to address the conference on Tuesday, will call for a Middle East free of nuclear weapons, specifically the disarmament of Israel. Kerry said Iran’s call for a nuclear-free Middle East is an “ambitious goal and fraught with challenges.” Russia’s Deputy Foreign Minister Sergei Ryabkov stated, “Israel has shown readiness for constructive steps to be taken.”

Israel has never publicly confirmed that it is in possession of any nuclear weapons.