The Democratic People's Republic of Korea and the Republic of Korea signed the Pyongyang Joint Declaration of September 2018 at an inter-Korean summit on Sept 19, which covers comprehensive inter-Korean cooperation and further denuclearization of the Korean Peninsula. The joint declaration marks a step forward in inter-Korean relations that will create opportunities and challenges for Pyongyang and Seoul, as well as Washington to different degrees.

The Pyongyang Joint Declaration is the diplomatic outcome of the DPRK's denuclearization efforts and pursuit of peace. In the declaration, Pyongyang has agreed to dismantle the missile engine test site and launching platform in Dongchang-ri in the presence of experts from other countries.

If Washington acts in the line with the US-DPRK joint statement of June 12, the DPRK will also shut down the Yongbyon nuclear facility. By allowing experts to observe the dismantling process, Pyongyang has appropriately responded to Washington's criticism that the DPRK has not taken enough denuclearization measures.

But to make the DPRK's efforts successful, the US has to take substantial corresponding measures in line with the Panmunjom Declaration of April 27 and the US-DPRK joint statement.

The problem for the ROK is that President Moon Jae-in's approval rating is at its lowest because of the poor results of his economic revival policies. But still the Pyongyang declaration is historic achievement for Moon.

However, it is difficult for Seoul to realize all the agreements. Cultural, environmental management, public health and medical care exchanges are not a big problem. But without the United Nations lifting the sanctions against Pyongyang, it will be impossible for the two sides to work together to establish railway connectivity, and build the Gaeseong industrial complex, Mount Geumgang tourism project, a west-coast special economic zone and an east-coast special tourism zone.

Besides, its alliance with the United States will create problems for the ROK as a mediator between Washington and Pyongyang. During the Pyongyang summit, DPRK leader Kim Jong-un attributed the success of his meeting with US President Donald Trump to Moon's mediation, and thus appreciated Seoul's role as a mediator between Washington and Pyongyang.

But since the US insists on comprehensive denuclearization, it may not agree with the DPRK's phased denuclearization plan. Moreover, the ROK is in a dilemma, because it signed the Pyongyang Joint Declaration to cease military hostilities while US Defense Secretary James Mattis said in August that the US has no plans to suspend joint US-ROK military exercises, which may evoke an angry response from the DPRK.

Although Trump welcomed the inter-Korean summit via Twitter, the olive branch delivered by the DPRK has created problems for the US before the midterm elections in November. When the US sought the DPRK's timetable for denuclearization, Kim wrote a personal letter to Trump seeking another US-DPRK summit and expressed his willingness to gradually dismantle the nuclear and missile test sites.

Pyongyang's substantial denuclearization efforts prompted Washington to reply that it was ready to hold another round of talks. Washington may hold talks with Pyongyang again after the midterm elections and might agree to cancel its joint military drills with the ROK only after ensuring the DPRK has fulfilled its denuclearization promises.

Even though the denuclearization of the Korean Peninsula is a long and complicated process, the Pyongyang declaration has further eased the tensions in Northeast Asia and is the right step toward restoring permanent peace on the peninsula. China's proposal that the US stop its joint military drills near the DPRK's waters and, in response, the DPRK take comprehensive denuclearization measures has played an important role in the peace process. Now, more countries should contribute to the peace process, in order to restore permanent peace on and promote the development of the peninsula and the region.

The author is an associate researcher at Northeast Asia Studies Institute, Jilin Academy of Social Sciences