Senate Foreign Relations Chairman Bob Corker has lifted a months-long hold on weapon sales to Gulf countries after it failed to encourage a resolution to the ongoing diplomatic standoff between Qatar and Saudi Arabia.

In a letter this week, the Tennessee Republican notified Secretary of State Rex Tillerson he was ending his eight-month blanket hold on lethal defense equipment sales to the six members of the Gulf Cooperation Council, which comprises Saudi Arabia, the United Arab Emirates, Kuwait, Qatar, Bahrain and Oman.

“Unfortunately, there still isn’t a clear path to resolving the GCC rift,” Corker wrote in the letter, which was first reported by Defense News. “Given that weapons sales are part of our security cooperation with these states, I am lifting the blanket hold on sales of lethal military equipment to the GCC and will resume informally clearing those sales.” 

Corker added his approval of weapon sales to Gulf nations was contingent on assurances from the Trump administration “that the purchasing state is taking effective steps to combat support for terrorism.”

GCC states are major buyers of U.S. weapons. Already this year, the Pentagon’s Defense Security Cooperation Agency has notified Congress of a proposed $500 million sale in missile system support to Saudi Arabia. 

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Last year, Riyadh bought nearly $17.2 billion worth of U.S. weapons systems, most of it in the form of intermediate-range ballistic missile defense systems while Bahrain acquired nearly $4 billion worth of F-16s and related equipment, patrol boats and missiles. The United Arab Emirates purchased $2 billion worth of Patriot missiles and Kuwait imported $1.2 billion in missiles, helicopters and tanks. Qatar made a $1.1 billion purchase for support services and equipment for its F-15 jets, according to the Forum on the Arms Trade, an advocacy organization concerned about the humanitarian implications of major weapons sales.

On a trip this week to the Middle East, Tillerson is trying to resolve the regional dispute, which kicked off last June when Saudi Arabia, the United Arab Emirates and Bahrain cut off diplomatic relations with Qatar and tried to blockade the small country.

The blockading nations said they were concerned about Qatar’s past negligence on terrorism financing and support for Islamist organizations, a region-wide problem that is not unique to Qatar.

Though the White House initially seemed to side with Saudi Arabia in the dispute, Tillerson for months has tried to take a more even-handed approach and has encouraged Saudi Arabia and the United Arab Emirates to resume diplomatic relations with Qatar.

Late last month, the administration hosted Qatar’s foreign and defense ministers for a symbolically important inaugural “Strategic Dialogue” with Tillerson and Defense Secretary James Mattis. The U.S. Treasury, Energy and Commerce secretaries also participated in the meetings, which were viewed as a public relations victory for the Qatar camp.

In a response letter to Corker, Tillerson said he appreciated the decision to lift the arms hold and that while “some operational improvements” have been seen toward resolving the Qatar dispute, no end is in sight.

“It is essential that the United States remain a reliable defense partner to the region,” Tillerson wrote, adding each of the countries involved in the dispute has been “a strong counter-terrorism partner.”