WASHINGTON—President Donald Trump will put his domestic economic and trade policies at the heart of a new national-security strategy that depicts the world as one of heightened rivalries and potentially dangerous competition.

The new strategy, with an emphasis on confronting unfair trade practices and precluding rivals from stealing American technology, holds potentially far-reaching implications for relations with China, which is described as a “revisionist power” that is seeking to undermine U.S. security and prosperity.

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