The England boss has had his England stars practising spot kicks for several months, both in the build up and during the World Cup itself.
The Three Lions have a woeful record in shoot-outs at major tournaments, having lost six and won just one of them.
England face Colombia in the last 16 in Moscow tomorrow and it could come down to another one to decide who goes through to the quarter-finals.
Rashford has never taken a penalty for Manchester United - but has no problem stepping up to the plate if Southgate wants him to.
The striker said: “It’s something we’ve been working on for a while now. It’s just about practice and repetition.
“Whilst we’ve been out here we’ve had one at the end of each session. It’s something you might not need, but we have to be prepared if it does go to penalties.
“It’s about if you feel comfortable taking one, which I do. That’s the way you go about it.
“But on the other side of it, if you don’t feel comfortable you have to be honest with yourself. That gives the team the best chance.
“I think he knows the players who are confident in those circumstances. It’s not going to be the same in a game - but I’d be willing to step forward.
Rashford admits scoring a penalty has nothing to do with luck and boils down to skill and dedication.
He added: “It’s about relaxing and composing yourself.
“Probably before the Christmas period we started putting a real focus on it. It’s something that’s continued to develop.
“It’s not down to chance. It’s definitely not chance. It’s a skill and every skill takes time to learn it and to perfect it.
“It’s just about being able, it’s a simple skill, but being able to perform it with pressure and everything around.”
