The militaries of Britain and Japan will "work more closely together" under a defense deal that British Prime Minister Boris Johnson announced during talks with his Japanese counterpart Thursday.

Johnson hosted Japanese Prime Minister Fumio Kishida at the British leader's 10 Downing St. residence. He noted the "strong stance" Japan has taken "against the Russian aggression in Ukraine" and drew a parallel with the security situation in Asia.

"There is direct read across from the actions of autocratic, coercive powers in Europe to what may happen in East Asia," Johnson said. "That's why we want to work more closely together."

Johnson's office said the deal will allow the armed forces of the two Group of Seven countries to deploy together for training, joint exercises and disaster relief.

The prime ministers agreed that "democracies around the world needed to stand in unity against authoritarian regimes," the office said after their meeting.

Kishida's first official visit to the U.K. as prime minister was marked with an overflight of London by three Royal Air Force planes.

Japan has condemned Russia's invasion and joined Western nations in imposing sanctions against Moscow. Japan also has supplied Ukraine with helmets and other non-lethal military aid.

Japan is concerned Russia's invasion of Ukraine could have an impact in East Asia, where China's military has grown increasingly assertive and threatened to unite with Chinese-claimed Taiwan by force if necessary.

Britain has announced an "Indo-Pacific tilt" in its foreign policy in the wake of its departure from the European Union in 2020, and sees Japan as its key East Asian ally.

Chris Hughes, a professor of international politics and Japanese studies at the University of Warwick, said Kishida's visit "will further consolidate a U.K.-Japan 'quasi-alliance' that has been worked on for the last decade or more."

He said U.K.-Japan relations are "becoming much stronger in security, but they will be tested by seeing how far Japan will be forthcoming to do more in security with the U.K. outside its own East Asia region and, likewise, how far the U.K. can sustain substantive cooperation with Japan outside its region with the ongoing Ukraine crisis."