Japan has shown reluctance to accept a proposal by South Korea to declare a formal end to the Korean War as a way to entice North Korea to negotiations on its denuclearization, diplomatic sources said Saturday, revealing gaps in the efforts also involving the United States.

Tokyo has been concerned that such a preceding conciliatory move would complicate its position for resolving the issue of past abductions by North Korea of Japanese citizens at the same time as that of the nuclear and missile development programs pursued by Pyongyang in defiance of U.N. Security Council resolutions, the sources said.

The United States and North Korea remain technically in a state of war as the 1950-1953 Korean War -- in which U.S.-led U.N. forces fought alongside the South against the North, backed by China and the Soviet Union -- ended in a cease-fire, not a peace treaty.

Japan expressed its concern last month when its senior official in charge of North Korea met with his U.S. and South Korean counterparts in Washington. The United States then did not make its position clear, according to the sources.

Combined photo shows (from L) Takehiro Funakoshi, head of the Japanese Foreign Ministry's Asian and Oceanian Affairs Bureau, Sung Kim, U.S. special representative for North Korea, and Noh Kyu Duk, South Korea's special representative for Korean Peninsula peace and security affairs. (Kyodo)

South Korean President Moon Jae In said in his speech at the U.N. General Assembly in September that he will seek to declare a formal end to the Korean War, naming China as a potential partner along with the two Koreas and the United States. He did not mention Japan.

At the senior officials' meeting on Oct. 19, Noh Kyu Duk, the South's special representative for Korean Peninsula peace and security affairs, underscored the need to proceed with the proposal by Moon, the sources said.

In response, Takehiro Funakoshi, head of the Japanese Foreign Ministry's Asian and Oceanian Affairs Bureau, said it is "premature" to discuss the proposal, citing that North Korea has repeatedly test-fired missiles, said the sources.

Sung Kim, U.S. special representative for North Korea, did not argue the pros and cons of the proposal, they said.

After the meeting, a Japanese government source only said the three agreed to continue diplomatic efforts in dealing with North Korea and working toward beefing up regional deterrence.

In its part, North Korea has said it will reject any South Korean proposal to declare a formal end to the war unless the United States withdraws its "hostile policy" toward the North, according to its state-run media.