For now, they've told him there isn't one, the president said Saturday in response to a question at the NATO summit in Lisbon.
"I understand people's frustrations," Obama said, while acknowledging that he's never had to undergo the stepped-up screening methods.
Passengers at some U.S. airports must pass through full-body scanners that produce a virtually naked image. If travelers refuse, they can be forced to undergo time-consuming fingertip examinations, including of clothed genital areas and breasts, by inspectors of the same sex as the passenger.
Obama said he's told the U.S. Transportation Security Administration: "You have to constantly refine and measure whether what we're doing is the only way to assure the American people's safety. And you also have to think through, are there ways of doing it that are less intrusive."
At this point, that agency and counterterrorism exports have told him that the current procedures are the only ones that they think can effectively guard against threats such as last year's attempted Christmas-day bombing. A Nigerian man is accused of trying to set off a bomb hidden in his underwear aboard a flight from Amsterdam with nearly 300 people aboard.
Obama said that in weekly meetings with his counterterrorism team, "I'm constantly asking them whether is what we're doing absolutely necessary, have we thought it through, are there other ways of accomplishing it that meet the same objectives."
For now it sounds like there aren't, and travelers will face potential pat-downs and scans.
"One of the most frustrating aspects of this fight against terrorism is that it has created a whole security apparatus around us that causes huge inconvenience for all of us," Obama said.
The new scans show naked images of the passenger's body, without the face, to a screener who is in a different location and does not know the identity of the traveler. The U.S. has nearly 400 of the advanced imaging machines deployed at 70 airports, expanding to 1,000 machines next year. So not all airports have them and not all travelers are selected for scans.
The hands-on searches are used for passengers who don't want those scans or when something suspicious shows in screening, or on rare occasions, randomly.
More on TSA's New Screening Procedures:
GOP's Mica: Ditch TSA, Hire Private Contractors
TSA Chief: Pat-Downs "For Your Safety"
9/11 Daughter: Airport Screening Foes Foolish
Senators and TSA Defend "Love Pats" at Airports
Religion Offers No Break on Airport Screening
Passenger Refuses Groin Check, Full Body Scan
Naked Body Scan Images Never Saved, TSA Says
Poll: Do New TSA Airport Screens Go Too Far?