Britain's choice of its next prime minister, to be announced at the end of the ruling Conservative Party's leadership race Sept. 5, is unlikely to change its global strategic partnership with Japan, but its engagement with the Indo-Pacific could stall due to Russia's war in Ukraine, observers say.

Regardless of whether Foreign Secretary Liz Truss, the front-runner, or her rival Rishi Sunak, a former chancellor of the exchequer, wins the race, the Ukraine crisis is likely to affect Britain's budget allocation and asset deployment to the region, creating a source of concern for countries such as Japan and the United States that are seeking to build a united front against an increasingly assertive China.

Scholars say both candidates are likely to base their diplomacy on Britain's 2021 Integrated Review of security, defense, development and foreign policy, which sets out a "tilt" to the Indo-Pacific. Truss has taken a more hawkish foreign policy stance than Sunak, including on China.