The United States is concerned about being 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. “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.