Top officials from the two nations are meeting in Washington this week to discuss tensions with China, Russia and North Korea and to plan for deterrence with U.S. troops and missiles.

WASHINGTON — U.S. and Japanese officials said on Wednesday that the two nations would expand their military cooperation, including improving Japan’s missile strike capabilities and making the U.S. Marine unit in that country more flexible for potential combat.

The changes come as both nations perceive greater threatening behavior from China and North Korea, as well as Russia. Those three countries have decades-long partnerships that they have recently affirmed in various settings, despite many nations’ condemnation of Russia over its war in Ukraine.

The United States and Japan have been working in recent years to strengthen their military alliance. On Wednesday, Antony J. Blinken, the U.S. secretary of state, and Lloyd J. Austin III, the U.S. defense secretary, met with their Japanese counterparts in Washington to discuss security issues and other matters. President Biden and Prime Minister Fumio Kishida of Japan are scheduled to meet in Washington on Friday.

“There is clear strategic alignment between the visions of President Biden and Prime Minister Kishida,” Mr. Austin said at a news conference after meetings on Wednesday.

He also praised Japan’s decision to increase its annual military spending. Last month, the Kishida administration released a new national security strategy in which Japan committed to spending 2 percent of its gross domestic product on its annual defense budget, a substantial increase that puts it in line with a standard set by the North Atlantic Treaty Organization.

The State of the War

• In the East: The head of the Wagner Group, a Russian mercenary force, claimed that his fighters had seized the town of Soledar, which has become a focal point in Russia’s monthslong campaign to gain control of the key eastern city of Bakhmut. If the claim were true, it would be the first significant Russian victory in months.
• Western Escalation: A cease-fire proposal seemingly aimed at splintering Western unity has instead been met with an escalation of military involvement by Ukraine’s allies.
• New Equipment: The Western allies’ provision to Ukraine of infantry fighting vehicles signals their support for new offensives in coming months. 
• Mr. Austin also affirmed Japan’s decision to invest more in “counterstrike capabilities,” meaning missiles that can be used for offensive operations. Japan has said it intends to buy hundreds of Tomahawk cruise missiles from the United States.