Japan's support would be the most important to the United States among its allies for defending Taiwan in the event of Chinese aggression, according to a U.S. think tank.
Given its geographic limitations, the United States would have to rely on support from allies in the Asia-Pacific region, and "above all Japan," the Council on Foreign Relations said in a recent report, titled "U.S.-Taiwan relations in a new era."
Japan hosts about 54,000 U.S. troops and the headquarters of some U.S. key units such as the Navy's 7th Fleet and the 31st Marine Expeditionary Unit, the report noted.
"The United States would find it nearly impossible to respond promptly and effectively to Chinese aggression against Taiwan without being able to call on" U.S. forces and its facilities in Japan, the New York-based think tank said.
U.S. fighter jets would be "unable to effectively join the fight" without the use of bases in Japan, and prior consultations with Tokyo would be needed for their deployment in combat operations.
To "pave the way for smooth prior consultations" during a Taiwan crisis, Japan and the United Sates "should have regular, serious dialogues," the report said.
Tensions have been mounting between Communist-led China and the United States over the self-ruled democratic island, which has been governed separately from Beijing since they split in 1949 as a result of a civil war.
China sees Taiwan as a renegade province to be reunified with the mainland, by force if necessary.
A conflict over Taiwan is widely seen as concern for Japan due to the proximity of its islands in the southwest -- including the Senkaku Islands, a group of East China Sea islets controlled by Tokyo but claimed by Beijing.
The report also said that the United States would need support from other regional allies, specifically naming Australia and the Philippines.
"Although U.S. allies are becoming increasingly open about their willingness to support U.S. intervention on behalf of Taiwan, more clarity is needed" so that Washington can discuss role-sharing with its allies and develop a "more integrated war plan," it added.
On the economic front, the report said China is likely entering a long-term slowdown and is not expected to achieve sustained growth due to U.S. policies including export controls on advanced technologies.
With a further downturn, Chinese President Xi Jinping could make further moves to "turn to the Taiwan issue to rally support" for the ruling Communist Party and his personal rule, according to the paper.
As Xi's third five-year term as the party's head approaches its end in 2027, "the risk of a conflict over Taiwan will grow," it said.
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