In early June, in cities across America, U.S. immigration agents arrested more than two dozen Chinese nationals with unfulfilled deportation orders, telling them that after years of delay, China was finally taking steps to provide the paperwork needed to expel them from the U.S.

But, not for the first time, China failed to provide the necessary documents, and three months later not one of those arrested has been deported, and many have been released from custody. They form part of a backlog of nearly 39,000 people Chinese nationals awaiting deportation for violating U.S. immigration laws, 900 of them classed as violent offenders, according to immigration officials.

The issue, which is likely to come up during a state visit to Washington later this month by Chinese President Xi Jinping, has further strained a U.S.-China relationship already frayed by tensions over economic policy, suspected Chinese cyber hacking and Beijing’s growing military assertiveness.

Meanwhile, China is pushing the U.S. on a different immigration issue: the return of Chinese citizens it says are fugitives from corruption investigations at home.

The June arrests, described by immigration lawyers, U.S. officials and some of the arrestees themselves, grew out of meetings aimed at speeding up a clogged process that has long frustrated the United States.

China has been extremely slow, U.S. immigration officials say, to provide the proof of citizenship necessary to send visa violators home. Some of the nearly 39,000 Chinese immigrants awaiting deportation have been under orders to leave for well over a decade, and the backlog continues to grow.

An apparent breakthrough came, officials say, at a March meeting in Beijing between Sarah Saldana, director of Immigration and Customs Enforcement (ICE), and Zheng Baigang, a top Chinese Public Security official. Their discussions produced a “memorandum of understanding,” agreed to by both countries, to help expedite the process.

In April, Department of Homeland Security Secretary Jeh Johnson traveled to Beijing, where his Chinese counterparts "agreed to begin repatriation flights from the U.S. for Chinese nationals with final deportation orders," said DHS Press Secretary Marsha Catron.

As part of that agreement, two Chinese officials traveled to the U.S. to interview those arrested in the June sweep, along with more than 50 others on the deportation list, including many with criminal convictions in the United States. China promised their cases would be resolved quickly.

In the past, an ICE official said, China has explained delays by saying it can be difficult to verify citizenship, a process that might require visits to distant villages and towns.

But one U.S. official suggested another reason for the holdups: "They do not want these people back.”

A senior Obama administration official told Reuters, ahead of Xi's visit, that the U.S. would like to see China move on this issue. “We have made that very clear, and pressed them to do so," the official said.

SWEPT UP

One of the immigrants detained in the recent sweeps was Daniel Maher, who was arrested as he left for work from his San Francisco Bay area home on June 2. Four uniformed immigration officials pulled up behind his car, he said, shackled his  wrists and legs and then drove him to a U.S. deportation office.

There, Maher says, he was searched along with 13 other Asian men and put into a prison jumpsuit. "We were told there was a 99.9 percent chance the travel documents were arriving to deport us to China," said Maher, who was born in Macau, a former colony of Portugal that  became a special administrative region of China after Maher immigrated to the United States. "I was told I would need a jacket, because the plane would be cold."

But Maher, who was convicted of holding up a San Jose, California auto parts warehouse in the 1990s and served a six-year term before being ordered deported in 2000, has since been released.

In a statement provided to Reuters, ICE said Maher was let go on August 14 “after it became apparent the agency would not be able to obtain a travel document in the foreseeable future to carry out its repatriation.”

U.S. frustrations over the massive deportation backlog come as Beijing is pushing for more help in tracking down and repatriating dozens of alleged fugitives living in the U.S. who are wanted in China as part of a widespread crackdown on corruption dubbed Operation Fox Hunt.

Officials in the U.S. put distance between the two issues, saying there will be no ‘quid pro quo’ agreement to provide Operation Fox Hunt suspects in exchange for cooperation on immigration violators. But they acknowledged that there are parallel discussion on the matters.

China, however, sees the two subjects as tied. In a statement, China's Foreign Ministry said: "China believes that there should be no double standards when it comes to the issue of handling the repatriation of illegal immigrants," urging “support for China's efforts to fight corruption."

U.S. officials say they are not averse to cooperation on Operation Fox Hunt, but that despite requests, Beijing has failed to produce the kind of evidence of criminality needed under American law to support deportation.

There is no extradition treaty between the U.S. and China, and Western governments have long been reluctant to hand over suspects because of a lack of transparency and due process in China's judicial system. In the past, Chinese government officials convicted of corruption have sometimes been sentenced to death.

BRIEF COOPERATION

Anoop Prasad, a San Francisco immigration attorney who represented Maher and others arrested in the June sweeps, says the Northern California detainees were transferred to an ICE facility in Adelanto, California, about a week after their arrest. There, they were each interviewed by two Chinese officials during a brief moment of cooperation between the two countries on the matter. They were also each ordered to fill out applications for Chinese passports.

"Those interviewed were selected because ICE determined that there was a significant likelihood of their removal in the reasonably foreseeable future," an ICE spokesperson said in a statement to Reuters.

And although no paperwork has yet come, the spokesperson added, "ICE expects the Chinese will honor their commitment to issue travel documents for those individuals confirmed to be Chinese nationals."

ICE acknowledges, however, that the backlog has been caused largely because of Chinese failure to provide documents and proof of citizenship.

Prasad said he believes his clients are being used as pawns in international diplomatic negotiations between China and the U.S., with America looking for help to reduce the backlog, and China wanting help in hunting down its corrupt fugitive officials, although Prasad admits he has no proof of that.

Prasad also questions why Maher was targeted. Since his release from jail in 2000, the attorney says, Maher, who is now married with a family, has turned his life around, working full time since 2005 and keeping all supervision appointments with ICE for the past 15 years.

U.S. officials say the two Chinese officials who conducted the interviews returned home in August.