The United States will clean up mustard gas bombs it left behind on an island in Panama where it tested them, a Panamanian official said Saturday.

"The Americans will be sending in a special team to carry out the cleanup" on San Jose island on Panama's Pacific side, under a deal expected to be finalized in a few months, said Tomas Cabal, with Panama's foreign ministry counterterrorism analysis unit.

Cabal said the six bombs should be cleaned up and removed by the US experts at some point in mid 2014.

The United States did testing on the island ahead of its military engagements in Japan (1939-1945) and Vietnam (1964-1975).

The Panamanian official said the US and Panama reached an agreement on the issue in April but it had not been made public.