Prime Minister Shinzo Abe vowed Thursday to strengthen Japan's alliance with the United States in the face of regional security concerns, including North Korea's nuclear and missile threats.

At the outset of his meeting with U.S. Pacific Command chief Adm. Harry Harris at the prime minister's office Abe hailed a recent visit by Donald Trump to Japan, saying he and the U.S. president have successfully demonstrated the strong bond between the two countries.

"As we are facing an increasingly severe security environment in the Asia-Pacific region, we would like to deepen our close cooperation to further enhance our response capability and deterrence under the Japan-U.S. alliance," Abe said during the talks, part of which was open to the media.

In response, the commander of the Hawaii-based command underlined the significance of a recent joint naval exercise in the Sea of Japan, saying it was "an example of how our militaries work together."

The two allies conducted the drill on Sunday involving three of the U.S. Navy's aircraft carriers and three escort vessels from the Japanese Self-Defense Forces, as part of a U.S. strike force exercise amid growing tensions surrounding the Korean Peninsula.

The meeting came after Abe and Trump renewed their pledge in their meeting last week to apply the maximum possible pressure on North Korea, to force Pyongyang to abandon its nuclear and ballistic missile development programs.

North Korea has stepped up its development of nuclear-tipped missiles capable of reaching the U.S. mainland in defiance of repeated international warnings.

In September, North Korea conducted its sixth and most powerful nuclear test and fired an intermediate-range ballistic missile over Hokkaido into the Pacific Ocean.