Although Machu Picchu has long been referred to as the “Lost City of the Incas,” there’s very little that now seems “lost” about the site that draws over half a million tourists each year.

Except, some Peruvians argue, for the Inca artifacts excavated from the site by Yale explorer Hiram Bingham III between 1911 and 1915 — artifacts which are currently housed at the Peabody Museum. Yale’s possession of these pieces has been a source of controversy in Peru and has sparked repeated attempts at negotiation between the University and the Peruvian government in recent years.

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A successful end to the disagreement seemed imminent in September, when representatives from Peru and Yale administrators signed a tentative agreement. But over four months later, there is still no telling when — if at all — the artifacts will be returned to Peru.

The terms of a memorandum of understanding signed by Yale and Peruvian officials visiting New Haven in September has, at once surprisingly and unsurprisingly, escalated political strife within Peru about the rightful ownership of the artifacts.

The political fallout from the tentative agreement has brought further talks between Yale and Peru to a virtual standstill, several sources familiar with the negotiations told the News this week.

Jose Koechlin, a Peruvian tourism entrepreneur who represents Machu Picchu on a task force overseeing the negotiations for Peru, said he does not expect any final deal to be reached in the near future.

“Soon is something I cannot foresee,” Koechlin said. “That a final agreement may be reached is wishful thinking.”

In September, Yale had agreed to recognize Peru’s title to the artifacts and to return most of the objects — and all of the museum-quality pieces — to Peru in short order. In addition, a co-sponsored exhibition of some artifacts was to travel the globe and eventually arrive at a museum near Machu Picchu that Yale would help Peru design. The memorandum gave the parties 60 days to sign a final agreement.

Despite these concessions, some research objects would remain at Yale over the next 99 years, University General Counsel Dorothy Robinson told the News at the time.

This last condition seems to have caused controversy within Peru and, at least in part, led to a 30-day extension to the 60-day deadline that the parties had set in September. But the extended deadline came and went over the winter, and the parties agreed to another extension of an undisclosed length.

Richard Burger, an archaeology professor at Yale who co-curated an exhibit of the artifacts in 2003, said discussions between Yale and Peru are ongoing at this point.

“The two sides are still talking,” Burger said. “We expect [the final agreement] will say something very close to the memorandum of understanding.”

University spokeswoman Helaine Klasky also said in an e-mail that Yale expects an ultimate resolution similar to the terms set forth in September, although Klasky said that “things sometimes happen a little more slowly than anticipated.”

But if Peru’s political opposition gets its way, any agreement with Yale would stipulate that all of the objects be returned to Peru immediately.

The fight over the artifacts came to a head during the tenure of former Peruvian president Alejandro Toledo. In an aggressive attempt to claim the objects, Toledo and his wife, Eliane Karp de Toledo, made the return of the Inca artifacts a priority during Toledo’s time in office, but negotiations at the time were hostile and Peru ultimately threatened to sue Yale over the objects.

The administration of current Peruvian president Alan Garcia, himself a former president who succeeded Toledo in 2006, has taken a more amicable approach to the negotiations.

But, under Peruvian law, a president cannot serve more than one consecutive five-year term. Even still, after stepping down, a former president can run for office again once an intermediary term has elapsed.

So, when Garcia’s term expires in 2011, Toledo could run again, a prospect that — given the bold stance his administration took on the subject — is part of the reason for why the artifacts remain on the front burner of Peruvian politics.

Karp de Toledo, herself an anthropologist and the leader of the effort to repatriate the artifacts, said in an interview with the News on Monday that the deal as negotiated in September was unfair to Peru.

“What’s the need for another century of research?” she asked. “This is a bad deal for Peru, and Yale has everything to gain from it. The final agreement should recognize that Peru has all the rights to all the pieces — all the pieces have to go back to Peru.”

Karp de Toledo said Peru can rightfully lay claim to all the objects because Bingham signed an agreement with the Peruvian government in 1912 in which he agreed to the eventual return of the objects. She criticized the Garcia government for letting political considerations trump Peru’s right to all of the objects.

“Garcia just wants a deal for the glory of it,” she said. “But it’s a bad deal for Peru, and it won’t be finished without a fight.”

But Hugh Thomson, a famed explorer and author of “A Sacred Landscape,” a recent book on Peru’s history, said by phone from England that the Peruvian opposition to the memorandum of understanding is surprising given Yale’s acknowledgement of Peru’s title to the objects and readiness to return most — if not all — of the objects in just a few years.

“From the Peruvian point of view, it seems to me that Yale capitulated,” he said.

No matter who is in office and what the terms of a deal, however, the return of the artifacts will remain controversial in Peru, said Barton Lewis, a contributing editor with National Geographic Traveler who has closely followed the story.

“It’s the kind of issue that can make careers,” Lewis said. “If you come off looking like you won — whatever that means — it would be a huge political victory.”

For its part, Yale is waiting for the Peruvian political process to play itself out. Burger said that Yale is eager to finish the negotiations, but the talks have been complicated by Peruvian politics.

“It is going back and forth because we can only control this side,” he said. “We cannot control the Peruvian side.”

But Koechlin, the Peruvian involved with the negotiations, emphasized that the question of ownership of the artifacts is not just a legal one but also a moral one, and it must not be just a political one.

“A legal question can be presented,” he said. “But it’s a question of the spirit of the law, of morality.”

Mariana Mould de Pease, a Peruvian historian who has long advocated for the return of the objects, said the fight will go on in Peru because the memorandum of understanding between Yale and Peru is not based on “historical facts.”

Mould de Pease noted that Peruvians gave Bingham the support he needed to get to Machu Picchu, which had been abandoned for centuries until Bingham brought it onto the world stage. But she added that Bingham had done a great service for Peru as well.

“No Peruvian could communicate Machu Picchu as well as Bingham did,” Mould de Pease said. “So we have to work together; we have to work with Yale.”

The lead negotiators for Peru, Minister of Health Hernan Garrido-Lecca and William Cook, of the Washington, D.C., law firm DLA Piper, both declined comment for this article.