A Beijing appeals court upheld Friday the eight-year prison sentence given to an American geologist for obtaining information on the Chinese oil industry, dimming hopes for his release in a case that has further strained U.S.-China relations.

The Beijing High People's Court, in a brief decision, refuted Xue Feng's arguments that the information he collected was commercially available and asserted the government's authority to classify material state secrets, said his lawyer, Tong Wei.

"They rejected all our arguments," Tong said outside the courthouse afterward.

An oil industry consultant, the 46-year-old Xue has already been in custody for more than three years. His case has vexed already troubled ties between Washington and Beijing and has been raised repeatedly in high-level meetings after Xue told American consular officials his interrogators physically mistreated him.

U.S. Ambassador Jon Huntsman, who attended Friday's ruling to underscore Washington's interest, questioned the charges against Xue and called for his release.

"This has been a long, difficult and painful ordeal for Xue Feng" and his wife and two children, Huntsman told reporters. "We ask the Chinese government to consider an immediate humanitarian release for Xue Feng, thereby allowing him to get back to his family and his way of life."

Already trying to ease strains over economic disputes, China's military buildup and its assertive foreign policy, the Obama administration had hoped Beijing would free Xue and deport him before Chinese President Hu Jintao's pomp-filled state visit to Washington last month.

Instead, members of Congress confronted Hu about Xue. The conservative Republican head of the House Foreign Affairs Committee, Rep. Ileana Ros-Lehtinen of Florida, and Rep. Kevin Brady, the Texas Republican who represents the suburban Houston district where Xue's family lives, separately pushed letters into Hu's hands urging Xue's release.

Ahead of the appeals ruling, his older sister, who still lives in China, despaired that her brother's treatment was now yoked to the larger diplomatic tensions between the two countries. "My brother is basically a sacrificial object, a funerary object, in the struggles of China-U.S. relations," Xue Ming said in an interview.

Ultimately, Xue's case came to symbolize China's arbitrary use of vague state secrets laws to protect powerful business interests, specifically the government's biggest oil companies.

Born in China and trained at the University of Chicago, Xue (pronounced shweh) was detained while on a business trip to China in November 2007. He was convicted of obtaining detailed information on the oil industry while working for the U.S.-based energy information consultancy now known as IHS Inc. Included was a database listing locations and other geological information for more than 32,000 oil and gas wells belonging to China National Petroleum Corp and China Petrochemical Corp.

At his trial and appeal, Xue and his lawyer never denied he obtained the information, but argued that such information was publicly and commercially available in most countries. In fact, the database had been advertised for sale on the Internet for several years. And, they said, the government only classified the database, power-point presentations and other documents after he obtained them.

In rejecting Xue's appeal, Tong said the court did not even consider that the database and other information was classified retroactively. Rather, Tong said, the court deferred to the government's unquestionable authority to declare information secret.

Xue reacted stoically to the verdict, Huntsman said, and the two talked briefly afterward.

"I think he was mentally prepared for it, disappointed of course. We all are," Huntsman said.

Held in a detention center during his trial and appeal, Xue will be moved to a prison in coming weeks. His avenues for appeal exhausted, his supporters are looking for a political solution.

Given the judiciary lack of independence in China's authoritarian, Communist Party-dominated system, high-profile cases like Xue's are particularly susceptible to government influence. Yet Chinese leaders have generally taken a harder line when foreign governments ask for clemency on high-profile legal cases because leniency is deemed politically risky and because a more powerful China can afford to reject such calls.

"They've decided to bow to whatever winds are blowing by becoming harder than hard," said John Kamm, a human rights campaigner the U.S. government has enlisted to try to win Xue's freedom.

Kamm said the options left for Xue include requests to commute his sentence and applications for medical parole. But, as with Friday's ruling, he said, the Chinese authorities are unlikely to be moved.

"In the words of the old country song, they've lived up to my low expectations," Kamm said.