HANOI, Vietnam » U.S. President Barack Obama on Monday lifted a decades-old arms export embargo for Vietnam during his first visit to the communist country, looking to bolster a government seen as a crucial, though flawed partner even as he pushes for better human rights from the one-party state.

Obama announced the full removal of the embargo at a news conference, saying the move was intended to step toward normalizing relations with the former war enemy and to eliminate a “lingering vestige of the Cold War.”

“At this stage both sides have developed a level of trust and cooperation,” Obama said, adding that he expected deepening cooperation between the two nation’s militaries.

Obama is seeking to strike this balance with Vietnam amid Chinese efforts to strengthen claims to disputed territory in the South China Sea, one of the world’s most important waterways.

Lifting the arms embargo will be a psychological boost for Vietnam’s leaders as they look to counter an increasingly aggressive China, but there may not be a big jump in sales. Vietnamese President Tran Dai Quang thanked Obama for lifting the embargo.

U.S. lawmakers and activists had urged the president to press the communist leadership for greater freedoms before granting it. Vietnam holds about 100 political prisoners and there have been more detentions this year.

The United States partially lifted the embargo in 2014, but Vietnam wanted full access as it tries to deal with China’s assertive land reclamation and military construction in nearby seas.

Vietnam has not bought anything, but removing the remaining restrictions shows relations are fully normalized and opens the way to deeper security cooperation.

After three days in Vietnam, Obama heads to Japan for an international summit and a visit to Hiroshima, where he will be the first sitting president to visit the site of the first atomic bomb attack.

He arrived in Hanoi, the capital, late Sunday, making him the third sitting president to visit the country since the end of the war. Four decades after the fall of Saigon, now called Ho Chi Minh City, and two decades after President Bill Clinton restored relations with the nation, Obama is eager to upgrade relations with an emerging power whose rapidly expanding middle class beckons as a promising market for U.S. goods and an offset to China’s growing strength.

Obama was greeted Monday by Quang at the Presidential Palace. Obama congratulated Vietnam for making “extraordinary progress.” He said he hopes the visit will show a continued interest in strengthening ties in the years to come.

Obama will make the case for stronger commercial and security ties, including approval of the 12-nation Trans-Pacific Trade agreement that is stalled in Congress and facing strong opposition from the 2016 presidential candidates.

The United States is eager to boost trade with a fast-growing middle class in Vietnam that is expected to double by 2020. That would mean knocking down auto, food and machine tariffs to get more U.S. products into Vietnam.

In Japan, Obama will attend a summit of the Group of Seven industrialized nations, where the uncertain global economy will be a top concern. They’ll also grapple with a full array of world challenges, including the fight against the Islamic State group in Iraq and Syria and the refugee crisis in Europe.

Obama will finish his trip in Hiroshima, where the U.S. dropped the atomic bomb that killed 140,000 people, ushering in the nuclear age seven decades ago. Another bomb killed 70,000 in Nagasaki three days later.

It will be a moment to reflect on the devastating costs of war and to try to give new impetus to the call for a nuclear-free world that Obama issued seven years ago in his first year as president. He has faced criticism, however, that his mere presence at the site of the a-bomb explosion could be viewed as apology for an act that many Americans see as justified.