Former U.S. President Barack Obama considered a pre-emptive strike on North Korea after it conducted its fifth nuclear test in September 2016, just days after lobbing three medium-range ballistic missiles 1,000 kilometers into Japan's exclusive economic zone, according to a book by Watergate journalist Bob Woodward released Tuesday.

The nuclear blast — and claims by Pyongyang that it could mount the new bomb on missiles that put allies Japan and South Korea within striking distance — had deeply troubled Obama, Woodward wrote in "Fear: Trump in the White House."

"Even with his intense desire to avoid a war, Obama decided the time had come to consider whether the North Korean nuclear threat could be eliminated in a surgical military strike," according to the book.