US Secretary of State Hillary Clinton joined scientists and aviation archaeologists to unveil the expedition, which will set out from Hawaii in July to probe underwater areas around the Phoenix Islands in Kiribati where they believe Earhart may have crashed 75 years ago.
"When she took off on that historic journey she carried the aspirations of our entire country with her," Clinton said, calling Earhart one of the "fearless optimists" who defined 20th century America.
"Even if you do not find what you seek, there is great honor and possibility in the search itself," Clinton said.
Earhart was the first woman to fly solo across the Atlantic Ocean and nonstop solo across the United States. The aviation pioneer was trying to fly around the world in a twin-engine plane when she disappeared.
The July mission is part of an effort by the International Group for Historic Aircraft Recovery (TIGHAR) to uncover Earhart's fate, an abiding mystery since she and navigator Fred Noonan left Papua New Guinea en route to Howland Island in the South Pacific on July 2, 1937.
TIGHAR Executive Director Ric Gillespie said that new analysis of a photo taken in 1937 near Nikumaroro island in present-day Kiribati appeared to show what could be the undercarriage of a Lockheed Electra airplane such as the one that Earhart was flying, emerging from a reef.
"It's a strong case, we think, but its circumstantial," Gillespie said. "Finding the plane would make it conclusive."
The US launch, which also featured Transportation Secretary Ray LaHood and was held in an elegant State Department reception room, played into the Obama administration's increasing emphasis on Asia-Pacific ties as it seeks to balance China's growing influence in the region.
The July phase will see TIGHAR researchers return to Nikumaroro aboard a University of Hawaii research ship equipped to map and investigate the underwater search area with small robotic submarines.
"There are some very smart people who think we're wrong about this. But there are some very smart people who think we're right about this," Gillespie said.
"The only thing we can do is make a best effort to go and search and look and see what we can find. And it's the searching that's important. It's the trying that's important."
There are numerous theories but thus far no definitive answers about Earhart's disappearance.
Gillespie's group is basing its hope in part on the 1937 photograph, which was taken by a visiting British sailor on a survey trip to the region several months after Earhart vanished.
New forensic analysis of the photograph backed up by an independent State Department study appears to reveal the Lockheed Electra's landing gear, which TIGHAR believes may indicate that the plane crashed on the island reef before eventually being washed deeper into the sea.
Gillespie is hoping that probes down the reef slope may reveal larger aircraft parts such as the engines lying in a dim "twilight zone" about 300m below the ocean surface.
Kiribati Foreign Secretarie Tessie Lambourne, who also attended Tuesday's event, said the small island nation hoped that interest in the Earhart investigation would spur concern about global warming and rising seas, which officials say could threaten the very existence of the nation of low-lying atolls.
Kiribati, a former British colony once known as the Gilbert Islands, won independence in 1979.
Oceanographer Robert Ballard, made famous by his discovery of the wreck of the Titanic in 1985 and who reviewed the latest Earhart project, said Gillespie's TIGHAR team appeared to have narrowed the "box" in which Earhart's wreckage might be found.
"If you ever want a case of finding a needle in a haystack, this is the top of the list," he said.
"He's got a reasonable box now and he's certainly got all the technology to do it. So all I can say is I wish him a fair wind and a following sea -- and a little luck."
Clinton's all-star tribute to Amelia Earhart was one of a string of events designed to highlight "Women's History Month" in March, part of her long-standing campaign to emphasize the contributions and potential of women and girls.
Saying that she herself had been discouraged as a young girl from an early dream of becoming a NASA astronaut, Clinton said people like Earhart accepted no such limitations.
"NASA may have said I couldn't go into space but nobody was there to tell Amelia Earhart she couldn't do what she chose to do," Clinton said.
