Foreign Secretary Tessie Lambourne of the Kiribati Republic has pledged that the vast Pacific archipelago would assist the latest effort to crack the mystery surrounding the disappearance of Amelia Earhart 75 years ago, as aviation enthusiasts from The International Group for Historic Aircraft Recovery are set to take on an underwater mission in July after they found a photograph of Kiribati's island of Nikumaroro.

Ric Gillespie, the group's executive director, said he came across a photograph of Nikumaroro taken in 1937 by a British expedition that was assessing the uninhabited island for potential settlement.

While the expedition was not linked to the Earhart mystery, Gillespie said a close analysis of a "blob" on the picture later made him realize it could be showing landing gear from Earhart's aircraft, the ill-fated Electra. He called the evidence "compelling, but circumstantial" and promised to search the entire area around Nikumaroro, AFP reports.

Earhart flew Electra in 1937 from Papua New Guinea on a mission to circumnavigate the globe over the equator. She and her navigator Fred Noonan were never seen again, even after a massive US search.

"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," 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."

Robert Ballard, the oceanographer who discovered the remnants of the Titanic in 1985, offered his support for the mission but said the area in which Earhart crashed was far vaster than the regions he had searched before.

"If you ever want a case of finding a needle in the haystack, this is the top of the list in deep-sea exploration," Ballard said.

The US government has offered assistance in analyzing the photographs and negotiating with Kiribati, but the search is funded by private donors, officials said.