WASHINGTON - The wife of a prominent Vietnamese human rights lawyer who was badly beaten by thugs and then detained by authorities appealed Tuesday for President Barack Obama to seek her husband's freedom when he visits Vietnam this month.

Vu Minh Khanh testified before a House panel. Hours earlier, the White House formally announced Obama's trip to Vietnam in late May, a sign of deepening relations four decades after the end of the Vietnam War.

But human rights remain a sore point. The authoritarian state is estimated to have about 100 political prisoners although it denies holding any.

Two Republican lawmakers called for Obama to demand the release of the detained lawyer, Nguyen Van Dai, and other prisoners of conscience.

"The administration seems eager to proceed with lucrative trade deals and to lift the ban on lethal arms sales to Vietnam, without imposing any real conditions," Rep. Chris Smith of New Jersey told the hearing.

"The situation is not improving. Human rights have got to be at the top of the president's agenda," said Rep. Ed Royce of California.

Speaking through an interpreter, Khanh said that her husband faces between three and 20 years imprisonment under a legal provision against "conducting propaganda against the state."

She said that Dai has been detained for nearly five months and has not been allowed access to family or defence lawyers. She said she's allowed to take him food twice a month at a detention centre in the capital Hanoi, but she has no idea if he gets it.

"In Vietnam, the public security force can do whatever they want," Khanh said.

She said that 10 days prior to Dai's Dec. 16 arrest, he was attacked and severely injured by "thugs with batons" after he conducted a human rights training session. She said her husband filed a complaint and the government said it didn't know who the assailants were.

She said that his release during Obama's visit would symbolize the president's support for human rights and democracy in Vietnam.

Dai has been detained before. He served four years in prison and four years of house arrest between 2007 and 2015.

The Vietnamese Embassy in Washington did not immediately respond to a request for comment.

The White House said that Obama will discuss with Vietnam's leadership how to advance co-operation on the economy, security and human rights. He will also meet with members of civil society.

Senior State Department officials were in Vietnam Tuesday, including top human rights envoy, Tom Malinowski, who last month said he raised Dai's case with Vietnamese officials amid concern over a recent spate of detentions of government critics.

Hanoi is eager for Obama to announce an end to a long-standing embargo on sales of lethal weapons to Vietnam as the two nations find common cause in countering a rising China.

News from © The Associated Press, 2016