Some previously undisclosed terms of a memorandum of understanding between Yale and the government of Peru over ancient Inca artifacts represent more significant concessions from Peru than were apparent in the summary of the memorandum released last September.

Those concessions — detailed in a copy of the memorandum obtained by the News this week — could be contributing to political disagreement within Peru that has delayed by more than three months a final agreement about the fate of the artifacts, which were excavated from Machu Picchu by Yale explorer Hiram Bingham III almost a century ago.

The memorandum, which was drafted and signed when a delegation from Peru visited New Haven in September, outlines the intention that any future legal action regarding the artifacts will be subject to Connecticut law and adjudicated by the U.S. District Court for the District of Connecticut. In perhaps a bolder stroke, the memorandum also dictates that the Peruvian government “shall release Yale from any legal claims to the Materials resulting from prior circumstances.”

The memorandum called for Yale and Peru to finalize within 60 days an agreement providing for the return of the artifacts to Peru, although that deadline passed without any agreement. Since then, the University has been pushing for a final agreement that would resemble the memorandum.

The agreement to pursue any legal claims in Connecticut may be beneficial to Yale, since the University would have an easier time in an American court proceeding than a Peruvian one, said Terry Martin, a professor of international law at Harvard Law School.

The terms have angered some in Peru — among them Eliane Karp de Toledo, Peru’s former first lady, who provided the memorandum to the News. Under the administration of her husband Alejandro Toledo, whose term expired in 2006, Karp de Toledo led the charge to repatriate the artifacts, even threatening Yale with legal action.

But Dorothy Robinson, University general counsel, said the memorandum represents a positive step for all parties involved.

“The [memorandum of understanding] is a win-win-win resolution for the government of Peru, for Yale and for the public,” she wrote in an e-mail. “I am hopeful that the final agreement which it contemplates will be signed very soon.”

The University, for its part, has said since September it is willing to acknowledge Peru’s title to the artifacts. But, in a move that has stirred controversy within Peru, Yale has asked to retain usufructuary rights to some non-museum-quality pieces for up to 99 years.

The question some Peruvians familiar with the negotiations have been asking, then, is what qualifies as a museum-quality piece and what does not. The University gave Yale archaeology professor Richard burger, who co-curated an exhibit of the artifacts at the Yale Peabody Museum of Natural History, the task of classifying the objects. Burger said he recently completed the inventory of the objects but does not know whether Peru’s government had been informed of his findings.

In assessing the pieces, Burger said, he acted in “good faith” and “erred on the side of Peru” by categorizing some pieces as museum quality simply because they are of special value to Peruvians.

Burger, who will curate a traveling exhibit of the artifacts under the terms of the memorandum, acknowledged that one joint consideration in the negotiations is the hope to construct a museum near Machu Picchu to house the pieces returning from the exhibit by 2011, the centennial anniversary of Bingham’s expedition.

But Karp de Toledo, now a lecturer in archaeology at Stanford University, said she is vehemently opposed to the memorandum of understanding, which she called a “bad deal for Peru.”

Specifically, Karp de Toledo took issue with the lack of Peruvian oversight of Burger’s inventory and the continued advisory role Yale will take in both the traveling exhibition and the museum. In addition, she said, while the memorandum notes that Yale has served “as steward of the Materials,” it does not include any concrete statement of thanks from Yale to Peru for having lent the University the artifacts for nearly a century.

The longer the negotiations take, Burger said, the shorter the international exhibition will be and the less time Peru and Yale will have to collaborate on a design for the museum. Such collaboration could definitively end the disagreement, he said.

Burger said he is confident the two camps will reach an agreement similar in content to the memorandum of understanding in the near future.

“One always has to be cautious, but the signs are good,” he said.

But as has historically been the case, Burger noted, political disagreement in Peru remains a roadblock to a final agreement.

“They have to get all their ducks in a row in Peru,” he said. “Once they do that, hopefully they’ll come up here and we’ll finish this.”

The negotiations between Yale and Peru were initially supposed to be completed within 60 days of the signing of the memorandum of understanding, but the two sides have agreed to several extensions that have allowed the parties to continue discussions.

Hernan Garrido-Lecca, Peru’s health minister and lead negotiator with Peru, declined to comment for this article.