Washington's reaffirmation on Tuesday that the truce remained in place helped steady investor sentiment after earlier market jitters over possible wider conflict.
The move built on gains signalled by rising S&P 500, Dow and Nasdaq futures, while falling oil prices also eased inflation worries and supported equities.
Markets had been watching the ceasefire after clashes in the Strait of Hormuz and missile attacks on the United Arab Emirates raised fears of regional escalation.
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