US President Joe Biden and Japanese Prime Minister Fumio Kishida meet at the White House on April, 10, 2014. (Photo: AFP)

"This is the most significant upgrade in our alliance since it was first established," Biden said after about two hours of talks in Washington which focused on the Indo-Pacific region, Gaza and Israel, Ukraine and Russia, North Korea and other world flashpoints.

Biden said their militaries will cooperate with a joint command structure and they will, together with Australia, develop a new air missile defense network.

The two leaders also announced that Japanese astronauts will participate in NASA moon missions.

Kishida said the two leaders pledged to uphold international order based on the rule of law.

Kishida will address the US Congress on Thursday and join Biden and Philippines President Ferdinand Marcos Jr. for a meeting.