The newly minted international maritime effort to defend against ongoing attacks on Red Sea shipping by the Iranian-backed Houthi rebels in Yemen is much larger than originally announced.

So far, 19 nations have signed onto what has been dubbed Operation Prosperity Guardian (OPG), instead of the initial nine that Defense Secretary Lloyd Austin introduced on Monday, Lara Seligman of Politico reported. That’s because most of the nations don’t want to go public, she reported, citing a senior administration official.