Tokyo, Japan - Japan and the US are planning to develop interceptors to shoot down hypersonic missiles by the 2030s under a contract signed by the two countries on Wednesday.

The plan, which will reportedly cost more than $3 billion, was first announced in August when the nations' leaders met at a summit with South Korea in Camp David outside Washington.

"In recent years, around Japan, missile-related technologies such as hypersonic weapons have improved dramatically," the defense ministry said in a statement about the agreement to jointly develop the so-called Glide Phase Interceptor (GPI).

"Strengthening interception capabilities against them is an urgent issue."

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The Japanese government has already included 75 billion yen ($480 million) in its 2024 budget for development of the interceptors.

"The US Japan Alliance is going hypersonic," US Ambassador to Japan Rahm Emanuel, who has a controversial track record in politics, wrote on X.

"Boosting deterrence in the Indo-Pacific means building the type of robust air and missile defense architecture we saw perform perfectly in Israel last month," he added, in apparent reference to Iran launching hundreds of drones and missiles at Israel amid the brutal siege of Gaza.

Hypersonic missiles fly at more than five times the speed of sound and have irregular trajectories, making them difficult to intercept.

The 75 billion yen is part of a record Japanese defense budget of 7.95 trillion yen approved last year, as tensions rise with China and North Korea.

Prime Minister Fumio Kishida has pledged to double defense spending to the NATO standard of 2% of GDP by 2027.

Japan has a pacifist post-war constitution, which limits its military capacity to ostensibly defensive measures, but it updated key security and defense policies in 2022, explicitly outlining the challenge posed by China.