The trade ministers of China and Japan exchanged protests over chip export controls and the detention of Japanese citizens at a meeting in Detroit last week, according to statements from both governments.

Chinese Commerce Minister Wang Wentao complained about Japan’s chip export curbs and a Group of Seven “attack” on China during a meeting with Japanese Trade Minister Yasutoshi Nishimura in Detroit on May 26, according to a ministry statement.

For his part, Nishimura called on Wang to release an employee of Japanese pharmaceuticals firm Astellas Pharma Inc who was detained in China in March, Japan’s Ministry of Economy, Trade and Industry said by email.

Read More: China Commerce Minister Protests Against Japan’s Chip Curbs

The meeting came amid strained ties between the Asian neighbors. Japan is trying to maintain business relations with its biggest trade partner, China, while not straying too far from the policies of its only formal security ally, the US.

China lodged a diplomatic complaint with Japan last week, after Prime Minister Fumio Kishida hosted the G-7 summit, at which the group of wealthy democracies vowed to “foster resilience to economic coercion” from China. Japan is also set to expand restrictions on exports of some leading-edge chip technology, while denying that the move is aimed at any particular country.

Wang told Nishimura that China is willing to work with Japan to promote cooperation on key economic and trade sectors. Ensuring the safety of Japanese company employees and maintaining a transparent business environment is important in pursuing economic cooperation, Nishimura told Wang.

The two ministers agreed to continue to stay in close touch, Japan’s METI said.