Japan has reportedly rejected a proposed trilateral meeting between Seoul, Tokyo and the U.S. regarding Japanese export restrictions on South Korea.

According to diplomatic sources on Sunday, the U.S. had proposed late last week that the three nations hold mid-level talks in Tokyo while U.S. Assistant Secretary of State for East Asian and Pacific Affairs David Stilwell is in Asia on official business.

South Korea was reportedly receptive to the idea while Japan demurred, citing scheduling conflicts.

Traction for a diplomatic settlement to Japan’s export curbs has thus far remained elusive. Last week, two officials from South Korea’s Ministry of Trade, Industry and Energy held a meeting with their Japanese counterparts in Tokyo, but only confirmed their differences.