Agriculture shippers are the latest group to call on President Barack Obama to intervene in the delays affecting West Coast ports.

In a letter to the Obama administration released Tuesday, the Agriculture Transportation Coalition of Washington, D.C., and its 61 signees said the delays at the West Coast ports, including Los Angeles and Long Beach, are having a “disastrous impact” on United States exports. Customers are cancelling their orders, the letter says, and getting new sources for their produce.

The letter includes stories from exporters of potatoes, fresh produce, hay, beef, pork, poultry, rice and chemicals describing the hardships they have faced since the delays began.

Additionally, the letter asks the President to consider assigning a federal mediator to assist in resolving union contract issues that have been reported as contributing to the delays.

Delays have also been attributed to an insufficient number of truck chassis and larger shipping containers.

The National Retail Federation wrote to the President on November 6 with similar concerns.