第二次世界大戰以來，美國構建了類型多樣的聯盟體系。當下，美國仍通過小多邊主義積極重塑聯盟體系。那麼，小多邊主義緣何成為美國重塑聯盟體系的重要路徑？文章在「權力平衡」、「威脅平衡」、「利益平衡」等聯盟理論的基礎上，通過「信任」與「威脅」的互動關係構建「信任－威脅」類型學框架以用於解釋美國聯盟的不同路徑與形態。文章認為，拜登政府主要選擇小多邊主義重塑以「四方對話」為代表的諸多彈性聯盟，試圖形成由美國主導的，涵蓋多領域、多地區、多層次的對華遏制彈性聯盟體系。美國選擇小多邊主義路徑重塑聯盟體系是由「外部威脅模糊－內部信任水準較高」條件決定的。

Since the World War II, The United States has constructed various types of alliance systems. Currently, Biden administration is actively reshaping the alliance system based on minilateralism. Why the United States prefers to operate on a minilateral basis? Based on the alliance theories such as “balance of power”, “balance of threat” and “balance of interests”, this paper constructs a “trust-threat” typological framework to explain the different paths and types of American alliance systems. The article argues that the Biden administration is trying to create or reshape a set of minilateral alliances in Indo-Pacific Region, including a multi-domain, multi-regional and multi-level elastic alliance system to contain China. The choice of minilateralism is the result of interaction between ambiguous threat perceptions and relatively higher level of trust.