US stock futures dipped Monday after President Trump vowed to impose 15% global tariffs following a Supreme Court ruling against his emergency levies. The high court struck down Trump's use of a 1977 emergency powers law for sweeping duties. Trump responded by employing a 1974 Trade Act section to implement temporary tariffs lasting up to 150 days, initially planning 10% before raising it to 15%.

Major US trading partners demanded clarity on the tariff implications. The European Commission insisted Washington honor its 2025 accord and called for "full clarity" on changing policies. China urged the US to abandon "unilateral tariff measures," emphasizing that cooperation benefits both nations. Customs will halt collecting struck-down tariffs Tuesday but offered no refund details.

Investors await Federal Reserve Governor Christopher Waller's speech on the economic outlook. Waller dissented from January's decision to keep rates unchanged, advocating for cuts. Oil prices dropped with Brent crude falling 1.3% to $70.39 and WTI declining 1.4% to $65.55, reversing gains as US-Iran nuclear talks progress, potentially easing Middle East supply concerns.