I was wondering if this was a legal move:

During Combat Phase I move Transports/troops and a cruiser into unnoccupied seazone 37 to do an amphibious assault on Malaya. The Assult fails (though it shouldn’t have :P) and my ships stay in seazone 37.
I continue with the rest of my attacks for that turn and during my movement phase I want to move ships into seazone 37 to protect my transports and cruiser. Is that allowed? My friend claims it is an illegal move because you have to declare all attack movements at the same time when concerning a single space, but I didn’t attack seazone 37 as there was no enemy ships in there, I simply did an amphibious assault. So shouldn’t I be able to move ships into there after the combat phase?
Please verify. Much appreciated. :)