A diplomatic thaw seems to have arisen on the Korean Peninsula as the Republic of Korea, Russia and the United States sent an invitation for talks to the Democratic People's Republic of Korea, amid preparations for an upcoming summit.

ROK President Moon Jae-in said on Wednesday that his country will deepen trust with the DPRK in the September summit during a ceremony to mark the 73rd anniversary of the peninsula's liberation from the 1910-45 Japanese occupation, according to the presidential Blue House.

Moon said he will take a determined step, through the meeting with the DPRK top leader Kim Jong-un, toward the complete denuclearization of the Korean Peninsula as well as a war-ending declaration and peace treaty.

"When the deep-rooted distrust between the two Koreas and between the DPRK and the US is lifted, the mutual agreement can be implemented," he said. "When peace is established on the Korean Peninsula along with complete denuclearization, economic cooperation can be carried out in earnest."

Moon proposed that the DPRK, China, Russia, Japan, Mongolia and the US jointly set up the so-called "East Asian Railroad Community" to connect railways across Northeast Asia via inter-Korean railroad links.

The president also sought to resume the inter-Korean industrial zone in the DPRK's border town of Kaesong and the tourism project in the DPRK's resort of Mount Kumgang.

After the high-level talks earlier this week, the neighbors agreed to hold the third Moon-Kim summit in Pyongyang before the end of September. Moon and Kim met in April and May at the border village of Panmunjom, promising to meet in Pyongyang this fall.

Russian President Vladimir Putin, on the same day, said he is ready to meet with Kim "at an early date", the DPRK's official Korean Central News Agency reported.

Putin expressed hopes to further develop "reciprocal cooperation including the realization of the tripartite project" that would also involve the ROK.

The US State Department said on Tuesday that inter-governmental talks between the US and the DPRK will become a "regular course of business", with denuclearization of the Korean Peninsula as the focus.

Li Chengri, researcher from Chinese Academy of Social Sciences, was optimistic about the future on the peninsula.

"Moon's visit will pave the way to ease the relationship not only within the peninsula, but also between the DPRK and the US," he said. "The key to the mitigation of DPRK-US relations lies in the progress of the DPRK's denuclearization and the corresponding measures of the US."

Xinhua contributed to this story.