US President zeroes in on North Korea, Iran threats

US President Donald Trump used his biggest stage Tuesday to warn of the nuclear threat from North Korea, as fears grow again in Washington that conflict may be looming.

In recent weeks, US officials have laid the groundwork for a pivot to strategies for a world of renewed great power competition with the likes of Russia and China.

In his State of the Union address to Congress and the nation, Trump described Moscow and Beijing as challenging "our interests, our economy, and our values." But he saved his harshest words for Iran and North Korea.

"North Korea's reckless pursuit of nuclear missiles could very soon threaten our homeland," he warned, implying he has a narrow window to respond to Pyongyang's ambition.

"We are waging a campaign of maximum pressure to prevent that from ever happening."

Singling out Iran and North Korea -- which along with Iraq formed his predecessor George W. Bush's "Axis of Evil" -- seemed calculated to raise the specter of new conflicts.

It came as a respected Korea expert, tipped to become Trump's ambassador to Seoul, revealed he had dropped out of the running and criticized the idea of a pre-emptive strike.

Secretary of State Rex Tillerson and Defense Secretary Jim Mattis have been pushing a diplomatic strategy to convince North Korean leader Kim Jong-Un to come to the table and negotiate away his nuclear arms.

But other senior figures have reportedly endorsed the idea of a "bloody nose" strike to damage Kim's nuclear sector and show the US means business, hopefully without provoking a wider war.

Victor Cha, a senior adviser at the Center for Strategic and International studies and until Tuesday a candidate for US ambassador to Seoul, rejected this in the Washington Post.

"A strike (even a large one) would only delay North Korea's missile-building and nuclear programs, which are buried in deep, unknown places impenetrable to bunker-busting bombs," he wrote.

Complacency and concessions

"A strike also would not stem the threat of proliferation but rather exacerbate it," he added, warning that Kim might try to sell nuclear weapons to "bad actors" for money or revenge.

Cha also pointed out that millions of South Koreans and tens of thousands of American expats and troops would be at immediate risk of a North Korean counterstrike.

"The president would be putting at risk an American population the size of a medium-size US city... on the assumption that a crazy and undeterrable dictator will be rationally cowed by a demonstration of US kinetic power," Cha wrote.

According to the Post, Cha's refusal to entertain the idea of a pre-emptive strike cost him his ambassadorship, and Trump's speech suggested he was in no mood for compromise.

"Past experience has taught us that complacency and concessions only invite aggression and provocation," he declared.

"We need only look at the depraved character of the North Korean regime to understand the nature of the nuclear threat it could pose to America and to our allies."

Trump also upped the ante in his stand-off with Iran, vowing US support for street protests against Tehran's clerical regime.

And again he compared himself favorably to his predecessor Barack Obama, suggesting that it had been a mistake not to back the failed 2009 Green Revolution in Iran.

"When the people of Iran rose up against the crimes of their corrupt dictatorship, I did not stay silent," he declared.

"America stands with the people of Iran in their courageous struggle for freedom," he promised, to applause from assembled lawmakers.

The president also highlighted gains made against the Islamic State group in Iraq and Syria, while warning that "there is much more work to be done" in the war against the jihadists.