China could invade Taiwan within the next six years, as Beijing accelerates its moves to supplant American military power in Asia, a top US commander said Tuesday. "I worry that they're (China) accelerating their ambitions to supplant the United States and our leadership role in the rules-based international order... by 2050," said Washington's top military officer in Asia-Pacific, Admiral Philip Davidson. "Taiwan is clearly one of their ambitions before that. And I think the threat is manifest during this decade, in fact, in the next six years," he told a US Senate committee. Taiwan split from China at the end of a civil war in 1949 and exists under the constant threat of invasion by the mainland.