One year ago, Democratic People's Republic of Korea (DPRK) leader Kim Jong Un and U.S. President Donald Trump held a historic meeting in Singapore, taking the "important first step" toward denuclearization and peace on the Korean Peninsula.

The two leaders signed a four-point joint statement pledging to "build a lasting and stable peace regime on the Korean Peninsula" and establish U.S.-DPRK relations.

Read more:

Full text: Trump and Kim's joint statement

Three sticking points in the U.S.-DPRK impasse

The whole world hailed the diplomatic breakthrough, as the two countries were moving towards each other with strong willingness of solving long-lasting issues. However, the momentum has cooled gradually since the signing of the joint statement with the two sides disagreeing on whether sanctions relief or denuclearization should come first.

In early May this year, two months after the collapse of Hanoi summit, the DPRK relaunched its missile tests, refused to continue talks with the U.S. and warned it would turn the joint statement into "a blank sheet of paper" unless the U.S. adopts a new approach. Within one year, U.S.-DPRK relations, as well as the Korean Peninsula nuclear issues, has once again reached an impasse with the possibility of returning to square one.

At the moment of the one-year anniversary of the Trump-Kim Singapore summit, it's a good time to check the progress each party has made in their commitments.

Here are the commitments reached by the two leaders and the progress made by each side in the past year.

Both parties agreed to the complete denuclearization of the Korean Peninsula, but the sticking point lies in how this should be done.

The DPRK has said it wants a "phased" simultaneous and "step-by-step" approach. In the latter half of last year, it sent a series of friendly and positive signals by partly realizing some of its commitments pending the U.S. taking corresponding measures. The approach also coincides with China's proposal which calls for dialogue and mutual respect to each other's concerns.

The United States, on the other hand, prefers a complete and verifiable denuclearization before it lifts sanctions and grants security guarantees to the DPRK.

The unilateral disarmament request and the U.S.' "gangster-like attitude" angered the DPRK, making negotiations more challenging.

The first twist came after Trump canceled Secretary of State Mike Pompeo's planned trip to the DPRK in August, 2018, due to limited progress made with respect to the denuclearization of the Korean Peninsula.

Although the two countries soon announced a second summit and Pompeo returned to the negotiating table in October, the fundamental differences on how to realize denuclearization still exist, paving the way for the collapse of the second Trump-Kim summit held in Hanoi in late February.

Then came the second twist, Trump's sudden departure from Hanoi summit without reaching an agreement surprised everyone and once again cast a shadow over the future of the Korean Peninsula.

According to Wang Peng, an associate research fellow at the Chongyang Institute for financial studies under Renmin University of China, the breakup reveals the divergent ways each side understands the issues. The requirements put forward by both parties are beyond the limits of what each is giving and promising at present.

The stalemate continues after the failed Hanoi summit and has intensified in the past three months. Its relaunch of two missiles on May 10 was interpreted by Republic of Korea (ROK) President Moon Jae-in as a manifestation of Pyongyang's frustration after the Hanoi summit and indicates that Pyongyang is losing patience.

The U.S. showed restraint towards DPRK's calculated message, as Trump said DPRK's "small weapons" does not breach its agreement with the U.S., reiterating his confidence in Kim, but seemed unwilling to compromise on his position on the deadlocked denuclearization talks.

The latest twist happened on May 24, when Pyongyang said nuclear talks with the U.S. "will never be resumed" unless the U.S. adopts a more "constructive" approach and threatened to turn the joint statement into a "blank sheet of paper" if the United States "does not come up with something new before it is too late."

The move sends a clear message to Washington and the whole world that they are preparing to return to their old path if their position cannot be respected.

Read more:

Pyongyang says no more nuclear talks unless U.S. changes stance

DPRK urges U.S. again to change attitude in nuclear talks

Considering the current stalemate, Tom Fowdy, a British political and international relations analyst, believes that the White House's "unwavering demand for unilateral capitulation to American terms" should be solely responsible for the deteriorating situation.

The Trump-Kim Singapore summit has certainly brought the two countries closer, but after a year of stalled talks and several twists, the future of U.S.-DPRK relations is seemingly becoming more uncertain.

Despite both sides stating that they were open to a third Trump-Kim summit, a complete denuclearization on the Korean Peninsula may be a far off dream.