President Barack Obama met Tuesday with Vietnamese communist party leader Nguyễn Phú Trọng in the hopes of strengthening ties between the two nations.

“The President also welcomes the opportunity to discuss other issues, including the Trans-Pacific Partnership, human rights, and bilateral defense cooperation,” the White House said in a statement.

The meeting came nearly four decades after the Vietnam War. Since that time, the two countries have made efforts to improve diplomatic relations. In just the past two years, Obama has met with Vietnam’s President Trương Tấn Sang and Prime Minister Nguyễn Tấn Dũng.

“Like in any relations between two countries in the world, Vietnam and the U.S. have differences on a number of issues, such as perception on democracy, human rights and trade,” Trọng wrote, according to NPR. “To resolve differences, I believe the most effective way would be open and constructive dialogues.”

While lawmakers hope the meeting will be used to address human right abuses in Vietnam, Trọng is hoping to get further help as his country deals with increasing aggression from China. The already troubled relationship between the two countries has gotten worse with China now building artificial islands in waters claimed by Vietnam.

“I do hope this is a chance for our two sides to have an open and frank discussion on issues where differences still exist,” Trọng told Bloomberg last week. “This would enhance mutual understanding, narrow the differences and gradually build up trust between us to add more substance and efficiency to long-term relations between our two countries.”

The U.S., Vietnam, and 10 other pacific nations have also been working to finalize a massive international trade deal known as the Trans-Pacific Partnership. Democrat lawmakers, unions and other critics have long argued the unfinished trade will not adequately address human rights violations in countries like Vietnam.

“The TPP must not go back on the progress made in recent years,” the AFL-CIO said on its website. “That’s why the AFL-CIO has been fighting hard for a strong labor chapter that ensures workers in any TPP country, including Vietnam, can exercise basic rights.”

Even Republican lawmakers, many of whom have supported the trade negotiations, want human and labor rights to be top priorities. They see the meeting with Trọng as a great time for the president to discuss the concerns.

“We are writing to urge you to make human rights improvements a top priority in your upcoming meeting with Mr. Nguyen Phu Trong,” several Republican senators said in a letter. “Vietnam remains a one-party state that treats many of its own citizens – particularly those who share the U.S. commitment to freedom and democracy — in ways that systematically transgress the minimum standards expected of any government.”

The letter was signed by Sens. Marco Rubio, Bill Cassidy, David Vitter, John Cornyn, John Boozman, James Lankford and Thom Tillis.

“The Trans-Pacific Partnership should not serve as simply another trade agreement,” the letter continued. “All nations in the TPP agreement should have a common commitment to religious freedoms and human values.”

Despite the concerns, the president has promised the trade deal will include provisions that benefit unions and improve labor standards among partner countries.

“So when you look at a country like Vietnam, under this agreement, Vietnam would actually, for the first time, have to raise its labor standards,” Obama argued in May. “It would even have to protect workers’ freedom to form unions — for the very first time.”

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