The United States is worried that its officials have been barred from attending the Aug. 7 trial in China of British investigator Peter Humphrey and his American wife Yu Yingzeng after the couple were arrested last year following work they did for British drugmaker GlaxoSmithKline PLC.
The concerns, voiced by the U.S. embassy in Beijing, adds a political dimension to the trial, which could become another thorny issue between the two economic powers, already tussling over areas ranging from cyber security and human rights to Chinese policy in the South China Sea.
"We are concerned that consular officers will not be allowed to attend Ms. Yu's trial in August 2014 despite the fact that under the 1982 bilateral consular convention between our two countries consular officials are permitted to attend such trials," U.S. Embassy spokesman Nolan Barkhouse said on Friday.
The British embassy also said it was "engaging" the Chinese authorities about the need for a transparent and fair trial. China's foreign ministry did not immediately respond to a request for comment.