The United States said Wednesday that attacks in space would invoke its defense treaty with Japan and announced the deployment of a more agile Marine unit on its ally's soil.

Weeks after unveiling plans to ramp up security spending, Japan sent its defense and foreign ministers to Washington where the two sides issued a statement vowing to "modernize the alliance in order to address the increasingly severe security environment."

The talks come two days before a visit by Prime Minister Fumio Kishida to Washington. Kishida is on a tour of G7 allies for security-focused talks, culminating in a meeting with US President Joe Biden on Friday.

The United States and Japan warned in their statement that "attacks to, from or within space present a clear challenge to the security of the alliance" that could invoke Article Five of their mutual defense treaty, which considers an attack on one an attack on both.

The talks finalized a plan by the United States to send a so-called Marine Littoral Regiment, a more agile unit that can operate defenses both by sea and air, to Okinawa, the southern Japanese island strategically close to Taiwan.

US Defense Secretary Lloyd Austin said the unit would be in place by 2025 from a reorganization of an existing artillery regiment.

"I think this is going to contribute in a major way in our effort to help defend Japan and also promote a free and open Indo-Pacific," Austin said, reiterating the US commitment to defend Japan including over islets contested by China.

UK, Japan sign major defense deal allowing troop deployments

On Wednesday, British Prime Minister Rishi Sunak and his Japanese counterpart Fumio Kishida signed what Downing Street called a "hugely significant" new defense deal allowing UK troops to deploy in Japan.

Sunak and Kishida signed the agreement at the Tower of London, with the UK leader telling his guest "the relationship between our two countries is stronger than ever, not just across trade and security but also our values."

The deal creates a legal basis for the deployment of British and Japanese troops on each others' territory for training and other operations.

Sunak's office called it "the most significant defense agreement between the two countries in more than a century."

"This Reciprocal Access Agreement is hugely significant for both our nations -- it cements our commitment to the Indo-Pacific and underlines our joint efforts to bolster economic security," the UK Prime Minister said.

Negotiations on the deal began in 2021. Japan signed a similar accord with Australia last January.

It is noteworthy that Japan has a pacifist post-war constitution, which limits its military capacity to ostensibly defensive measures. But last month, the Japanese government approved plans to hike defense spending to two percent of GDP by 2027, up from the traditional one percent level, and claimed that China poses the "greatest strategic challenge ever" to its security.

In Paris, Kishida and French President Emmanuel Macron pledged deeper ties, with the latter promising to maintain "joint actions in the Pacific" and France's "unfailing support" against North Korea's alleged "violation of international law." 

Japan holds the G7 presidency this year and Kishida has vowed the group will maintain support for Ukraine, which is thought to have been on the agenda in his talks with Sunak.

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