The United Nations on Wednesday called out inefficiencies in the operation of a deal allowing Ukraine Black Sea grain exports, but did not lay blame for a backlog of more than 100 ships in Turkish waters waiting on travel approval and inspections.

Under the deal agreed by Russia, Ukraine, Turkey and the United Nations in July, ships are inspected in Turkish waters on their way to and from Ukraine. The four parties work together to approve and inspect ships traveling under the agreement.

“The United Nations urges all parties to work to remove obstacles for the reduction of the backlog and improve operational efficiencies,” it said in a statement.

U.S. Ambassador to the United Nations Linda Thomas-Greenfield last week accused Russia of a “deliberate slowdown of inspections,” saying that 5 million tonnes of food a month should be moving under the agreement.

The Russian U.N. mission did not immediately respond to a request for comment on Thomas-Greenfield’s remark.

“We have been pushing to get more inspections. We’ve been pushing to make sure that the inspections proceed quickly and thoroughly,” deputy U.N. spokesman Farhan Haq said. “Everything has to be done with the cooperation of all the parties, and we’re trying to do everything we can to move it faster.”

Since November, three inspection teams have been deployed daily and so far this month have concluded 5.3 inspections a day, said the United Nations, adding: “In the last two weeks, the average waiting time of vessels between application and inspection is 21 days.”

It said some 3.7 million metric tonnes in Ukrainian exports moved under the deal in December, up from 2.6 million in November, while during the past two weeks nearly 1.2 million metric tonnes of exports shipped.

The package deal also includes facilitating Russia food and fertilizer exports, including ammonia, and the United Nations has been trying to negotiate a restart of Russian ammonia shipments via a pipeline to a Ukrainian Black Sea port.

“The parties negotiating on how to get ammonia to the market through the Togliatti/Yuzhny pipeline are still in discussions and are yet to reach an agreement,” the United Nations said.

Ammonia is a key ingredient in nitrate fertilizer. Russia’s Feb. 24 invasion of its neighbor had stalled Ukraine’s Black Sea exports of foodstuffs and also shut down the ammonia pipeline.