Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

SEOUL, South Korea — North Korean leader Kim Jong Un used his New Year’s Day address to warn the U.S. not to test him while striking a softer tone with South Korea, including the possibility of sending a delegation to next month's Winter Olympics.

"The entire United States is within range of our nuclear weapons, a nuclear button is always on my desk. This is reality, not a threat," Kim said in the annual address. "This year, we should focus on mass-producing nuclear warheads and ballistic missiles for operational deployment. These weapons will be used only if our society is threatened."

In September, North Korea conducted its sixth and most powerful nuclear test. Pyongyang tested a total of 23 missiles last year, including 15 that were nuclear-capable. The November launch of which appeared to be an intercontinental ballistic missile, or ICBM, flew farther than any of Kim's previous tests. The North claimed it could reach anywhere in the mainland U.S.

Analysts say that based on the current evidence it's hard to prove or debunk North Korea's claim that it can now hit faraway American targets such as New York or Washington, D.C.

Kim's regime has yet to prove publicly that it’s able to put a small enough warhead on a missile that wouldn’t impede its flight. It’s also unclear whether North Korea has developed a vehicle capable of protecting a warhead from intense heat upon reentering the atmosphere.

Related: Kim ready to 'press the button' at 1st sign of attack, defector says

However, experts say North Korea’s capabilities shouldn’t be discounted.

The Morning Rundown Get a head start on the morning's top stories. This site is protected by recaptcha

"Even though the ICBM technology may be somewhat incomplete, Kim is asserting that because he has a nuclear deterrent, the U.S. should not make military threats but engage with North Korea towards peaceful co-existence," said Dr. Koh Yu Whan, a professor of North Korea studies at Dongguk University in Seoul.

In Kim’s address Monday, overtures for reconciliation were not aimed at the U.S., but South Korea.

After a year in which President Donald Trump and Kim repeatedly traded jabs — largely via Twitter on Trump’s end — the young North Korean leader didn’t mention the U.S. commander in chief by name in his speech.

But in a move that could ease tensions on the Korean Peninsula, Kim proposed immediate talks with Seoul over North Korea taking part in the Winter Olympics in PyeongChang.

“North Korea’s participation in the Winter Games will be a good opportunity to show unity of the people, and we wish the games will be a success,” Kim said.

Seoul responded warmly and welcomed the prospect of talks. A spokesman for South Korea’s presidential office said it has been open to the idea as long as talks are related to improving inter-Korean ties and building peace.

A pair of North Korean figure skaters have qualified for the Games that begin on Feb. 9, and South Korean President Moon Jae-in has made it clear he wants North Korea competing in PyeongChang. Last month, he told NBC News he hopes the 2018 Olympics “will be able to promote the peace between the North and South Korea and become an Olympics for peace.”

Moon is also hoping Washington’s cooperation to help ensure a peaceful Games without interruption from North Korea. The president said he suggested to Washington delaying annual joint military drills until after the Olympics and Paralympics end in March. According to Moon, the U.S. is reviewing his suggestion.

John Delury, an associate professor of East Asian studies at Yonsei University's Graduate School of International Studies, said delaying the drills should be a “no-brainer.”

“The one concrete overture [in Kim’s speech] is about the Olympics. And it’s a positive one. And we know it’s very important for Seoul,” Delury added.

Pyongyang regularly denounces large military drills involving the U.S. and South Korea as a rehearsal for war.

In exchange for not just a delay, but a full halt of the drills, North Korea has offered to freeze its nuclear and missile programs.

North Korea has said in public statements that it wants an official end to the Korean War. The conflict was halted by a 1953 armistice but no peace treaty has been signed. It also wants nothing short of full normalization of relations with the U.S. and to be treated with respect and as an equal in the global arena.

Washington has also been the driving force behind greater international sanctions against North Korea, including tougher economic measures approved by the U.N. Security Council on Dec. 22 that target oil imports.

CORRECTION (Jan. 2, 12 p.m. ET): An earlier version of this article misstated the number of missiles North Korea tested in 2017. The country tested 23 missiles, not 18.