"There's a tremendous expectation of Olympic success," Troy said.

"That's a tremendous burden. I don't think that's going to change.

"We would like to exceed and do better than we have ever done before.

"At the same time it's an extremely competitive world and US athletes always have a target on their backs."

USA Swimming executive director Chuck Wielgus announced that Troy would guide the men and McKeever would direct the women.

Both were 2008 Beijing Olympics assistants and guided United States teams at August's Pan Pacific Championships.

McKeever, the first woman to be named a main coach for any US Olympic swim team, coaches at the University of California.

"I'm incredibly honoured to have been selected," McKeever said.

"I hope some day being a female on an Olympic staff isn't as noteworthy as maybe it is now.

"I'm looking forward to being a head coach and being able to put my touch on the experience, my touch as being Teri rather than being male or female."

Troy (pictured), who coaches at the University of Florida, will guide Michael Phelps, the superstar who won a record eight gold medals at Beijing, and Ryan Lochte, who has had the best results since China.

American swimmers won a total of 31 medals in Beijing, including 12 gold.

"We have a tremendous base for 2012," Troy said.

"With athletes like Michael Phelps and Ryan Lochte, I think the opportunity to be fantastic is there for the United States."

Troy said a key factor for both coaches will be building relationships with top swimmers and their individual coaches over the next 18 months to lay the groundwork for building teamwork and support at London.

"There's a tremendous wealth of athletes to keep track of over the next 12 to 18 months," Troy said.

McKeever said a women's squad of veterans such as Natalie Coughlin will be pushed to their best by new young talent and that their past experience in guiding Olympians did not necessarily mean no changes would come going forward.

"I will voice my opinion on things," McKeever said.

"Whether that changes anything from what we have done remains to be seen.

"I think we're in really great shape."