North Korean leader Kim Jong Un reaffirmed on Tuesday his resolve to completely denuclearize the Korean Peninsula, but warned he may have to take an alternative path if the United States continued to force Pyongyang into unilateral action.

In his New Year address, Kim said he was willing to meet U.S. President Donald Trump again at any time to achieve denuclearization, and urged Washington to take unspecified corresponding action to speed up the stalled process.

North Korea, however, would have "no option but to explore a new path in order to protect our sovereignty" if the United States "miscalculates our people's patience, forces something upon us and pursues sanctions and pressure without keeping a promise it made in front of the world," Kim said in his nationally televised address.

The comments are likely to fuel growing skepticism over whether Pyongyang intends to give up the nuclear weapons program that it has long considered essential to its security.

Kim and Trump vowed to work towards denuclearization and build a "lasting and stable" peace regime at their landmark summit in Singapore in June, but little progress has been made since and satellite images have indicated continued activity at North Korea's nuclear and missile facilities.

Pyongyang has demanded Washington lift sanctions and declare an official end to the 1950-53 Korean War in response to its initial, unilateral steps toward denuclearization, including dismantling its only known nuclear testing site and a key missile engine facility.

U.S. officials say those steps can be easily reversed and have not been verified, and Washington has slapped additional economic sanctions on the impoverished country. Washington halted some large-scale military exercises with Seoul, although smaller drills continued.

Kim called for South Korea to "completely stop" joint military drills with the United States involving strategic assets, while multilateral negotiations should be pursued to build a permanent peace regime on the Korean Peninsula.

"Now that North and South Korea decided to take the path of peace and prosperity, we insist that joint military exercises with outside forces should no longer be allowed and deployment of war equipment such as outside strategic assets should be completely stopped," Kim said.

Analysts said Kim's message sent clear signals that North Korea is willing to stay in talks with Washington and Seoul this year — but on its own terms.

"North Korea seems determined in 2019 to receive some sort of sanctions relief ... The challenge, however, is will Team Trump be willing to back away from its position of zero sanctions relief?" said Harry J. Kazianis at the Washington-based Centre for the National Interest.

"Kim's remarks seem to suggest his patience with America is wearing thin."

The televised speech is closely watched as a rare public appearance for the young leader, setting the tone for his domestic and foreign policies for the year ahead.

After racing toward the goal of developing a nuclear-tipped missile capable of hitting the United States in 2017, Kim used last year's speech to call for defusing tensions and improving ties with the South, and a shift in focus toward economic development.

That resulted in a dramatic detente last year, including three summits with South Korean President Moon Jae-in, and the historic meeting with Trump in June.

In this year's 30-minute speech, Kim spent more than 20 minutes highlighting his new focus on the economy.

Kim said inter-Korean relations have now entered a "completely new phase", and he is willing to resume key joint economic projects with the South — the factory park in Kaesong and tours to Mt. Kumgang — without conditions.