Prime Minister Shinzo Abe became Japan's second-longest-serving prime minister Saturday, exceeding Eisaku Sato, his great-uncle, who served for 2,798 days in the 1960s to 1970s.

Abe, who has now become the country's longest-serving leader after World War II, stands a good chance of winning the title of all time in November, trailing the current record holder Taro Katsura, who served 2,886 days.

Following the first shorter stint between 2006 and 2007, since his 2012 return, Abe, whose government has focused on boosting the deflation-mired economy, has secured relatively solid public support as he has no strong rivals.

Still, he is far from achieving his long-held goal of amending the pacifist Constitution for the first time since it took effect in 1947.

As the ruling coalition and other like-minded lawmakers in favor of constitutional reform lost the two-thirds majority in an upper house election in July, Abe is now urging opposition parties to engage first in parliamentary debate over the supreme law. Such a majority is required to start the revision process.

On the foreign affairs front, Abe faces a host of challenges. Japan has yet to make any tangible progress in dealing with issues such as North Korea's abductions in the 1970s and 1980s of Japanese nationals and signing a postwar peace treaty with Russia by resolving a territorial dispute.

Sato, who is now the third-longest-serving Japanese leader after Abe, is known for achieving Okinawa's reversion to Japan from the United States in 1972 and signing a treaty that normalized ties between Japan and South Korea in the postwar era.

Decades later, the 1965 treaty is at the center of a diplomatic dispute between Tokyo and Seoul, and ties between them have recently sunk to the worst in years.

South Korea's top court last year ordered Japanese firms to compensate for wartime forced labor during Japan's colonial rule of the Korean Peninsula from 1910 to 1945. Tokyo has maintained that it and Seoul had agreed in 1965 to settle the issue of compensation "finally and completely."

Mutual trust is also at stake as the two nations have locked horns over trade policy, first triggered by Tokyo's tightening of export controls on some South Korea-bound materials used in making crystal displays and semiconductors.