By Jon Herskovitz

AUSTIN, Texas (Reuters) - China has set a Sept. 19 trial date for a U.S. businesswoman it has held since March 2015 for suspected spying, and is suppressing evidence that weakens its case, the woman's husband in Texas said in a statement on Thursday.

Vietnam-born Sandy Phan-Gillis, from Houston, a U.S. citizen of Chinese ancestry, was arrested by Chinese authorities in March last year when she visited China as part of a trade delegation from Houston.

She has been held since then. This week, Beijing officials said she has been formally charged with spying.

This brought new attention to her case just ahead of a visit to China by U.S. President Barack Obama, who will arrive on Saturday for a G20 summit in the city of Hangzhou. Obama is scheduled to hold bilateral meetings with Chinese President Xi Jinping on Saturday.

"The charges are absolutely false," her husband Jeff Gillis said, adding he wants Obama to ask for her release when he meets Xi.

Gillis said a key contention of the charges was that his wife went on a spy mission to China in 1996. Her U.S. passport from that time shows she made no trip to the country, he said.

The Chinese Consulate in Houston is refusing to legally acknowledge that it contains no entry or exit visas from China, preventing it from being used as evidence at trial, he added.

Officials from the Chinese Embassy in the United States and the Chinese Consulate in Houston were not immediately available for comment.

"Based on our understanding, Phan-Gillis, because of her suspected crimes of espionage, has been charged according to law by the relevant Chinese department," Chinese Foreign Ministry spokeswoman Hua Chunying told reporters at a regular briefing earlier this week.

State Department spokesman John Kirby said at a briefing in Washington on Thursday that U.S. officials have repeatedly pressed Chinese authorities to provide further details of the case and give U.S. consular officers full and unrestricted access to her as required by international conventions.

"We (remain) deeply concerned about Ms. Phan-Gillis’ welfare. We continue to monitor her case closely," Kirby said.

(Additional reporting by Arshad Mohammed in Washington, DC; Editing by Bernadette Baum and Alan Crosby)