WASHINGTON (Reuters) - The United States has renewed a waiver for Iraq to continue importing Iranian electricity, a State Department official said on Sunday, but this time for a shorter period of 30 days, adding that Washington would be reassessing whether to renew again once a ‘credible government’ is formed in Iraq.

“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 U.S. 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 90 or 120 days.

The United States has insisted that oil-rich Iraq, OPEC’s second-largest producer, move towards energy self-sufficiency as a condition for its exemption for importing Iranian energy.

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.

Ties between Washington and Baghdad have been strained as the United States said it was disappointed that Iraqi forces have failed to protect the U.S. forces stationed in Iraq. They have come under multiple rocket attacks this year alone, for which the United States blames the Iran-backed militia.

U.S.-Iranian relations have been bitter since the Islamic Revolution toppled the U.S.-backed Shah of Iran in 1979 and ushered in an era of theocratic rule. Tensions flared up after President Donald Trump pulled out the 2015 Iran nuclear deal and reimposed U.S. sanctions that have crippled the Iranian economy.

Worsening tensions, a Jan. 3 U.S. drone strike in Iraq killed Qassem Soleimani, the head of Iran’s elite Quds Force. It also killed Abu Mahdi al-Muhandis, who founded Iraq’s Shi’ite Kataib Hezbollah militia after the 2003 U.S.-led invasion.

The State Department official said the waiver granted by Pompeo applied only to electricity and referred to the Treasury Department for transactions related to Iranian natural gas imports.