"The Secretary granted this brief extension of the waiver to allow time for the formation of a credible government," a State Department official said, referring to US Secretary of State Mike Pompeo, and added that the waiver would expire on May 26.
Washington has repeatedly extended the exemption for Baghdad to use crucial Iranian energy supplies for its power grid, for periods of 45, 90 or 120 days.
Iraq relies on gas and electricity imports from Tehran to supply about a third of its power grid, crippled by years of conflict and poor maintenance.
Earlier this month, Iraq's president named intelligence chief Mustafa al-Kadhimi as prime minister-designate, the third person tapped to lead Iraq in just 10 weeks as it struggles to replace a government that fell last year after months of deadly protests.
"Once that government is in place, the Secretary will reassess whether to renew the waiver and for how long," the State Department official said.
David Schenker, Assistant Secretary for Near Eastern Bureau at the State Department in a briefing earlier this month had praised Kadhimi's work as the head of intelligence.