WASHINGTON (Yonhap) -- North Korea delivered a "private message" to the U.S. government on its plan to conduct another nuclear test in 2009, along with its intent to enrich uranium, a former top White House official said in his book recounting the Obama administration's policy on East Asia.

"In April the North Koreans sent Washington a private message making several threats: to explode a nuclear device, to develop an ICBM capable of reaching the United States, to enrich uranium to enable them to develop a light-water reactor," Jeffrey Bader, who served as senior director for East Asian affairs on the National Security Council from January 2009 till April 2001, said in his memoir made public on Thursday. The 188-page book is titled "Obama and China's Rise: An Insider's Account Of America's Asia Strategy."

The U.S. responded with a "strong warning" about the consequences, Bader said, but the North went ahead with its second-known nuclear test about a month later.

When the North test-fired a long-range missile, which it claims was a satellite, in April 2009, the U.S. "considered a range of military options to deal with the highly unlikely contingency that the North's missile might be equipped with a warhead and be aimed at American territory," said Bader, who now works as a senior researcher at the Brookings Institution.

His recount shows how serious the mood in Washington was at that time.

He also disclosed a behind-the-scenes story of former U.S. President Bill Clinton's trip to Pyongyang in 2009 to bring two detained female American journalists back home.

The U.S. initially proposed the dispatch of former Vice President Al Gore, the head of the news outlet employing the journalists, but the North demanded a visit by Clinton.

White House officials initially rejected the idea out of concern that Pyongyang would treat Clinton's arrival as a kind of state visit for propaganda and President Obama agreed with his advisors.

"Pressure continued to build to resolve the matter. The State Department was in regular contact with the journalists' parents, who had agreed to keep a low profile for the sake of a quiet resolution, but their patience was running out," he said. "Before long, they were likely to go public with a campaign, against not only the North Koreans but also against the Obama administration."

In the end, Secretary of State Hillary Clinton suggested that Washington send her husband, Bader said.