EA have announced through their blog
that the Medal of Honor beta for the Xbox 360 has been delayed but should be available next week.
The PC and PS3 beta's will continue as normal on June 21st, although people who own Battlefield: Bad Company 2 and have pre-ordered MOH can start playing today.
"We are extremely disappointed about this, but want to assure you that we are dedicated and determined to delivering all of you this awesome multiplayer experience as soon as possible. However, we are excited to extend the beta to make up for lost time!"
More information on the beta can be found at the official site