Croatia canceled a $500 million sale of 12 F-16 fighter planes from Israel on Thursday due to the United States denying an Israeli request to execute the deal.

“Unfortunately, the conditions were not ready, and we were not able to implement the project due to unforeseen circumstances beyond our control,” said Udi Adam, the director general of the Israeli Ministry of Defense. “Croatia could not influence this outcome and cannot be held responsible for the failure.”

Then-U.S. Secretary of Defense James Mattis rejected a request last month from Israeli Prime Minister Benjamin Netanyahu to soften the U.S. conditions, including returning the planes to their initial state prior to Israeli upgrades.

The Croatians previously said that they would nullify the agreement if they couldn’t receive the “upgraded” Israeli type of the F-16s. Its defense ministry gave Israel a Jan. 11 deadline to clear the deal with the U.S. State Department.

The F-16 is a single-engine, supersonic multi-role fighter aircraft originally developed by General Dynamics for the U.S. Air Force.

U.S. Secretary of State Mike Pompeo reportedly supported the agreement, but told Netanyahu last month that Mattis blocked it.

Pompeo and Netanyahu met in Brazil this month, where the latter “received almost everything [he] wanted” except approval to proceed with the sale, a senior official told Israel’s Channel 10 news.