BILLINGS, Mont. (AP) — Dozens of American Indian communities on Tuesday joined an initiative to return millions of acres of reservation land to the control of tribal governments as U.S. officials warned the $1.9 billion program will run out of money before the task is completed.

A total of 63 reservations in 16 states in the West and Midwest were added to the Interior Department's "Land Buyback Program," bringing the total number involved to 105.

The land purchases resulted from legal settlement with American Indians led by Elouise Cobell of Montana, who said the U.S. mismanaged trust money held by the government on behalf of hundreds of thousands of Indians.

The program has paid more than $742 million to landowners since 2013. Looking ahead to its 2022 expiration date, Interior officials indicated the remaining money will be gone and they'll need to go back to Congress to work out a solution.

The 1.5 million acres restored to tribes to date represent the "low-hanging fruit" of relatively inexpensive land, said John Dossett, general counsel for the National Congress of American Indians. Land that's more valuable — for example, because it has timber, oil or other natural resources — could cost more and take longer to acquire, he said.

"Tribes were hoping for this $1.9 billion obviously, and it's a very significant down-payment, but it's not going to be enough," Dossett said.

The goal is to consolidate land that has split or "fractionated" ownership, freeing it up for economic development or other uses by tribal governments.

An 1887 law, the Dawes Act, split tribal lands into individual allotments that were inherited by multiple heirs with each passing generation.

As a result, parcels of land on some reservations are owned by dozens, hundreds or even thousands of individual Indians. That can make property all but impossible to sell or develop.

There are nearly 3 million fractional land interests owned by 245,000 people spread over 150 reservations that are eligible for the program. Many of the purchases to date comprised large parcels on Western reservations with a large land base. That includes at least 200,000 acres each on the Crow, Fort Belknap and Fort Peck reservations of Montana and the Pine Ridge and Cheyenne River reservations of South Dakota.

Interior Deputy Secretary Michael Connor said in a Tuesday statement that time limits and the money available from the Cobell settlement "do not provide enough to consolidate all fractional interests across Indian Country."

Connor has been told by Interior Secretary Sally Jewell to craft options by early July for extending the life of the program.

That could include bumping back the expiration date, adding more money or some combination of the two, said Interior spokeswoman Treci Johnson.