Navy use of the canal is infrequent, with about 40 vessels transiting annually, excluding the service’s aircraft carriers, which are too large. Allowing free access would reportedly save the U.S. about $13 million each year, according to the WSJ report.

Panamanian President José Raúl Mulino on Thursday denied the U.S. State Department’s claim that his country had agreed to allow U.S. government vessels to transit the Panama Canal for free, an assertion that has upended the two countries’ talks on the waterway.