HANOI (REUTERS) - A young couple with matching expressions stare nervously into the camera with deep brown eyes. He, a Vietnamese student, has just met the love of his life. She, a North Korean, is forbidden to love him back.

It was in 2002, 31 years after Mr Pham Ngoc Canh took that first photo with Ms Ri Yong Hui, that the two were finally allowed to get married, when North Korea took the rare step of allowing one of its citizens to marry a foreigner.

"From the moment I saw him, I was so sad because I felt it would be a love that could never be realised," said Ms Ri, 70, speaking from the small Soviet-era apartment she and Mr Canh, 69, share in the Vietnamese capital, Hanoi.

Now enjoying freedoms in Vietnam that would be impossible in North Korea, Mr Canh and Ms Ri are hoping the upcoming summit between United States President Donald Trump and North Korean leader Kim Jong Un in Hanoi will help end hostilities with Pyongyang.

"If you're a North Korean, you want to see this resolved. But politics is complicated," Ms Ri said.

"When people first heard Kim Jong Un decided to meet Trump, they expected reunification to happen soon. But that's hard to realise in just one or two days. I hope things work out well."

Today one of Asia's fastest growing economies and integrated into the international community, Vietnam has been touted as a model for isolated and impoverished North Korea to follow.

Back in 1967, as Vietnam and the US were locked in war, Mr Canh was one of 200 Vietnamese students sent to North Korea to gain the skills the state needed to rebuild itself once the war was over.

Several years later, during a chemical engineering apprenticeship at a fertiliser factory on North Korea's east coast, Mr Canh spotted Ms Ri working in a laboratory.

"I thought to myself, 'I must marry that girl'," said Mr Canh, who eventually plucked up the courage to approach Ms Ri and ask for her address.

She obliged: Her friends had told her one of the "Viet Cong" working at the factory looked just like her and she was curious.

"As soon as I saw him, I knew it was him," she said. "He looked so gorgeous."

"Until then, when I had seen so-called handsome guys, I hadn't felt anything, but when he opened the door, my heart just melted."

But there were challenges. Until this day in North Korea and in Vietnam at the time, relationships with foreigners are strictly forbidden.

GUERRILLA ACTION

After the couple exchanged several letters, Ms Ri agreed to let Mr Canh visit her at home.

He had to be careful. A Vietnamese comrade had been beaten when he was found with a local girl.

Dressed in North Korean clothes, Mr Canh embarked on the three-hour bus journey and 2km walk to Ms Ri's home - a trip he repeated monthly until he returned to Vietnam in 1973.

"I went to her house secretly, just like a guerrilla," said Mr Canh.

Upon his return to Hanoi, Mr Canh felt disillusioned. Though he was the son of a high-ranking cadre, he refused to join the Communist Party, forgoing the bright future the state had planned for him.

"I just couldn't agree with a socialism that stops people from loving each other," he said.

Five years later, in 1978, the Vietnamese chemical engineering institute Mr Canh was attached to organised a trip to North Korea.

He asked to join and managed to meet Ms Ri. But every time they saw each other, Ms Ri said, she became more heartbroken at the thought that they might never meet again.

He had brought with him a letter he had written to the North Korean leadership, begging for permission for them to marry.

"When she saw the letter, she asked: 'Comrade, do you intend to persuade my government?'" recalled Mr Canh, who never sent the letter and instead asked Ms Ri to wait for him.

THE WEDDING

Later that year, Vietnam invaded Cambodia, triggering a border war with China. With North Korea on the side of Beijing and Phnom Penh, the couple stopped writing.

"My mother was crying while caring for me," said Ms Ri. "I think she knew that I was lovesick."

In 1992, Mr Canh again managed to get himself on a trip to North Korea as a translator with a Vietnamese sporting delegation, but couldn't meet Ms Ri. When he returned to Hanoi, he found she had sent him a letter.

She still loved him.

In the late 1990s, North Korea was gripped by a devastating famine and a desperate delegation from Pyongyang visited Hanoi to ask for rice. Vietnam, which by then had undertaken major economic and political reforms and re-engaged with the West, refused.

Mr Canh was so concerned for Ms Ri and her people that he raised seven tonnes of rice in donations from friends to send to North Korea.

It was an act of generosity which finally paved the way for he and Ms Ri to reunite: The North Koreans learnt of Mr Canh's act and agreed he could marry Ms Ri and live in either country - provided Ms Ri maintained her North Korean citizenship.

In 2002, the two finally married in the Vietnamese embassy in Pyongyang and settled into their new life together in Hanoi, where they still live today.

"In the end, love beat socialism," said Mr Canh.