WASHINGTON -- US Democratic presidential candidate Joe Biden would likely pursue a step-by-step approach toward North Korea with reciprocal benefits for both sides if elected, a former US State Department adviser on nonproliferation and arms controls said Tuesday.

Robert Einhorn, now serving as a senior fellow at the Brookings Institution, declared US President Donald Trump's maximum pressure campaign has failed.

"A Biden administration won't give up the ultimate goal of complete denuclearization of North Korea, but it may be prepared to approach that long-term goal step by step with reciprocal benefits to each party at every stage of the process," he said in a webinar hosted by the Washington-based think tank.

"Kim Jong-un is unwilling to give up his nuclear capability altogether, and he may even be unwilling to accept meaningful limits on nuclear and missile programs, and the intrusive measures -- verification measures -- needed to ensure confidence in compliance," he added, referring to North Korea's reclusive leader.

In a recently published book, "Rage," based on his 18 private interviews with Trump, Washington Post journalist Bob Woodward noted the second Trump-Kim summit ended without a deal as Kim offered to give up only one nuclear facility while Trump demanded all five facilities and locations the US knew about at the time.

The second Trump-Kim summit was held in Hanoi in February 2019.

The leaders' first meeting was held in Singapore in June 2018.

Trump, despite his talks with Kim stalling since their second summit in early 2019, has often claimed credit for preventing what he claims would have been an imminent nuclear war with the communist North.

Einhorn agreed Trump's maximum pressure campaign deserved some credit for doing "major harm" to the North Korean and Iranian economies, but insisted he "utterly failed to compel these countries to capitulate to US demands."

The former State Department adviser said the Trump administration failed to rein in the nuclear ambitions of North Korea and Iran for three reasons.

"First, it acted alone without the support of key countries, even America's closest allies. Second, it did not align ends and means. It generated tremendous economic leverage, but pursued overly ambitious unachievable negotiating objectives. And third, it underestimated the determination and resilience of countries prepared to pay an enormous price to protect what they regarded as vital interests," he told the virtual seminar.

He said he did not think a Biden administration would make the same mistakes.

"It would pursue negotiations with North Korea more cautiously because the likelihood of success with North Korea would be lower, and the political minefields dealing with North Korea are even more treacherous than those dealing with Iran," said Einhorn.

Under a Biden administration, however, the North Korean and Iranian issues may not be given the top priority, at least in the early stage of the administration, he noted.

"Top priority, at least at the start of the administration, would be domestic -- the pandemic, the economy, restoring civility, racial justice," he argued.

Also in foreign policy, a Biden administration would first seek to reestablish the United States' global leadership and regain its respect from other countries, partly by rebuilding its key alliances, including those with South Korea and Japan, added Einhorn.

"I believe it would first want to rebuild South Korean and Japanese' confidence in US security assurances, and that includes not threatening to reduce US military forces if our allies don't pay enough."

Einhorn noted a Biden administration would also be willing to work with China and Russia, whose cooperation, he said, will be required for "any positive outcome on North Korea."

With regard to US efforts to deter missile threats from North Korea, Einhorn insisted the US would have to rely on threats of retaliation, unless it rids the communist state of its nuclear and long-range missiles.

"It's clear that the North Koreans are going to do everything they can to ensure they have a reliable ability to attack the United States homeland," he said, referring to Pyongyang's recently unveiled new intercontinental ballistic missile that he said is "probably" capable of carrying multiple warheads to the US mainland.

"We can try...with all kinds of exotic technologies, to stay ahead of the game, but I think at the end of the day, unfortunately, we're going to have a situation where we will rely on the threat of retaliation with US offensive strategic forces to deter a North Korean nuclear attack," said Einhorn.

"It's unfortunate, but sooner or later, that's the world we're going to have to live in." (Yonhap)