WASHINGTON -- Amid nuclear tensions between Washington and Pyongyang, US President Donald Trump took the extraordinary step of honoring a North Korean defector Tuesday as he delivered his State of the Union speech before Congress.

Ji Seong-ho, who escaped from North Korea in 2006, was given a place of honor just seats away from First Lady Melania Trump, as the president told the his story to lawmakers near the end of his 80-minute speech.

Trump recounted the suffering of Seong-ho, who had a foot and a hand amputated after a North Korean train rolled over him in 1996.

Malnourished and badly disabled, he was later tortured by the regime for a short visit to neighboring China, before escaping and walking on crutches across swathes of China and Southeast Asia in a journey to freedom.

"Today he lives in Seoul, where he rescues other defectors, and broadcasts into North Korea what the regime fears the most: the truth," Trump said.

"He has a new leg, but Seong-ho, I understand you still keep those crutches as a reminder of how far you have come. Your sacrifice is an inspiration to us all."

As members of Congress rose to their feet, so did Seong-ho, thrusting his crutches triumphantly into the air and eliciting a roar of approval from lawmakers.

"Seong-ho's story is a testament to the yearning of every human soul to live in freedom," Trump added.

The striking image of a North Korean defector receiving a standing ovation was one of the memorable moments of Trump's speech.

Other symbolic honored guests were seated nearby, including the parents and two siblings of Otto Warmbier, an American student who died last year shortly after being released from detention by North Korean authorities.

"You are powerful witnesses to a menace that threatens our world," the president said of the grieving parents.(AFP)