WASHINGTON, Nov. 7, 2017 -- President Donald J. Trump warned North Korean dictator Kim Jong Un tonight not to underestimate the will and power of the United States and urged him to rid his country of nuclear weapons.

Trump, who spoke before the National Assembly in the South Korean capital of Seoul, said the United States stands with South Korea in opposing the North.

The president, in the midst of a trip through Asia, said North Korea has pursued its nuclear weapons and missile programs "in defiance of every assurance, agreement and commitment it has made to the United States and its allies."

North Korea promised to freeze its plutonium program in 1994. It did not. "In 2005, after years of diplomacy, the dictatorship agreed to ultimately abandon its nuclear programs and return to the treaty on nonproliferation," Trump said. "But it never did. And worse, it tested the very weapons it said it was going to give up."

In 2009, the United States again offered to negotiate with North Korea. The regime answered by sinking the South Korean navy ship Cheonan, killing 46 sailors. "To this day, it continues to launch missiles over the sovereign territory of Japan and all other neighbors, test nuclear devices, and develop ICBMs to threaten the United States itself," the president said.

'We Will Defend Our Common Security'

"The regime has interpreted America's past restraint as weakness. This would be a fatal miscalculation," Trump said. "Today I hope I speak not only for our countries, but for all civilized nations when I say to the North: Do not underestimate us. And do not try us. We will defend our common security, our shared prosperity, and our sacred liberty."

The 38th parallel that separates North and South Korea is the line "between peace and war, between decency and depravity, between law and tyranny, between hope and total despair," the president said.

The line has been drawn by other oppressors in the past, and holding that line is the choice free nations have made through history, Trump said. "We have learned together the high cost of weakness and the high stakes of its defense," he added. "America's men and women in uniform have given their lives in the fight against Nazism, imperialism, communism and terrorism. America does not seek conflict or confrontation. But we will never run from it."

Trump said the United States will not let itself or its allies be blackmailed or attacked. "We will not allow American cities to be threatened with destruction," he said. "We will not be intimidated. And we will not let the worst atrocities in history be repeated here on this ground we fought and died so hard to secure."

Trump flatly stated that the time for excuses is over and that now is the time for strength. "If you want peace, you must stand strong at all times," he said. "The world cannot tolerate the menace of a rogue regime that threatens with nuclear devastation."

Seeking Cooperation From Russia and China

He specifically called on Russia and China to join the rest of the world in isolating the North Korean regime in Pyongyang. He asked all nations to fully implement U.N. Security Council resolutions, downgrade diplomatic relations with the regime, and sever all ties of trade and technology. "It is our responsibility and our duty to confront this danger together, because the longer we wait, the greater the danger grows and the fewer the options become," he said.

Trump addressed the North Korean leader directly, saying the weapons he is building are not making his regime more secure, but rather are putting it in grave danger. "Every step you take down this dark path increases the peril you face," Trump said.

Despite all the crimes committed by the regime since 1950, the nations of the world will offer a path to a better future for the North Korean people, the president said. "[The path] begins with an end to the aggression of your regime, a stop to your development of ballistic missiles, and complete, verifiable, and total denuclearization," he said.

South Korea stands in stark contrast to the North, Trump said. "In just a few decades, with only the hard work, courage, and talents of your people, you turned this war-torn land into a nation blessed with wealth, rich in culture and deep in spirit," he said. "You built a home where all families can flourish and where all children can shine and be happy."

South Korea is an independent, confident, peace-loving and respected nation, and is a strong ally of the United States, Trump said. "We are nations that respect our citizens, cherish our liberty, treasure our sovereignty, and control our own destiny," he added. "We affirm the dignity of every person and embrace the full potential of every soul. And we are always prepared to defend the vital interests of our people against the cruel ambition of tyrants."