As the Israel-Iran conflict continues unabated and U.S. negotiations with Iran have yet to produce a deal, six B-2 stealth bombers are reportedly headed to Guam, and it’s possible they’re carrying bunker-busting bombs thought to be capable of destroying Iran’s underground Fordow nuclear complex.

The bombers apparently refueled after launching from Missouri, suggesting they launched without full fuel tanks due to a heavy onboard payload, which could be bunker-buster bombs.

The B-2 can carry two 15-ton bunker-buster bombs—which only the U.S. possesses. Experts say the bombs could be critical to targeting Iran’s most heavily fortified nuclear site: Fordow.