WASHINGTON — C.I.A. analysts studying the geopolitical gamesmanship now at play over Iran’s nuclear program have expensive and highly classified tools at their disposal, but one of their best sources is free and readily available: the public utterances of Iran’s supreme leader, Ayatollah Ali Khamenei.

Like much of the information about Iran’s secretive and enigmatic government, Ayatollah Khamenei’s remarks are sometimes contradictory, and always subject to widely different interpretations. But as negotiations over the country’s nuclear program begin on Saturday in Istanbul, efforts to divine where Ayatollah Khamenei really stands on the nuclear issue have taken on critical importance.

Underscoring Ayatollah Khamenei’s direct involvement in the issue, Iran’s chief negotiator, Saeed Jalili, arrived in Turkey with a new title: “personal representative of the supreme leader.”

“Dismissing what he says out of hand is not useful for us,” said Greg Thielmann, a former State Department analyst. “I think the U.S. can exploit what he says.”

Ayatollah Khamenei, who is not only the leader of Iran’s government but also the final authority on Islamic law, often uses religious language when he talks about the nuclear issue, which can jar Western analysts trying to gauge the meaning of such strong statements. With tensions over the nuclear program rising in February, he used that language to signal his opposition to nuclear weapons. “Iran is not seeking to have the atomic bomb, possession of which is pointless, dangerous and is a great sin from an intellectual and a religious point of view,” he said.

Then last month Ayatollah Khamenei was reported to have said that “we do not possess a nuclear weapon, and we will not build one.” Ayatollah Khamenei has also issued a fatwa, an Islamic edict, against the acquisition of a nuclear bomb by Iran.

But those comments are not only at odds with some of Iran’s behavior but also with what Ayatollah Khamenei has said in the past. For evidence, analysts can point to remarks Ayatollah Khamenei made last year that it was a mistake for Col. Muammar el-Qaddafi of Libya to give up his nuclear weapons program.

Referring to Colonel Qaddafi, Ayatollah Khamenei said that “this gentleman wrapped up all his nuclear facilities, packed them on a ship and delivered them to the West and said, ‘Take them!’ ”

“Look where we are, and in what position they are now,” he added.

Complicating matters further, some analysts say that Ayatollah Khamenei’s denial of Iranian nuclear ambitions has to be seen as part of a Shiite historical concept called taqiyya, or religious dissembling. For centuries an oppressed minority within Islam, Shiites learned to conceal their sectarian identity to survive, and so there is a precedent for lying to protect the Shiite community.

Inside the government, each new reported remark by Ayatollah Khamenei is scrutinized for nuanced changes in tone and emphasis. If anything, one senior former intelligence official said, analysts should be studying the remarks even more carefully, to remain open to possible alternative assessments of Iran’s behavior. “I think, looking back, maybe we should have taken his statements more into account, particularly the religious statements,” the former official said.

Dennis B. Ross, who stepped down last fall after coordinating Iran policy for the White House, said that ultimately Ayatollah Khamenei’s comments revealed a leader who was stubborn and nationalistic, yet who still may be hedging his bets about whether to acquire a nuclear bomb.

“The value of looking at Khamenei’s statements is that he has written a lot and said a lot,” Mr. Ross said. “There is a certain consistency about what he has said.” His language, Mr. Ross added, shows that “he has always viewed the nuclear program as a sign of Iran’s technological advance, and that this is the way Iran will achieve independence.”

“He sees our opposition to the nuclear program as a function of our efforts to deny them their independence,” Mr. Ross said. “At the same time, in his recent statements he says that nuclear weapons are a sin, and he previously issued a fatwa. But he still presides over a nuclear program.

“And so if you are a C.I.A. analyst, you can see the context here,” Mr. Ross added. “This is someone who has consistently said if you make concessions, you only whet the appetite of the arrogant powers. He is committed to the nuclear program, but he is also someone who is obviously centered on preserving the system that he has created, and he has left himself an out, in that he says he isn’t interested in nuclear weapons. And that creates a context in which to evaluate the choices he may make.”

The history of Iran’s nuclear program offers evidence that can be used for several interpretations of Ayatollah Khamenei’s statements and behavior. Ayatollah Ruhollah Khomeini, the leader of the Iranian revolution that overthrew the pro-Western Shah Mohammed Reza Pahlavi in 1979, originally believed that it was anti-Islamic to build nuclear weapons, and he ended the secret nuclear weapons program that the shah had begun.

But the brutal Iran-Iraq war that lasted from 1980 to 1988 changed the Iranian thinking about nuclear weapons. Iraqi forces under Saddam Hussein used chemical weapons against ill-prepared Iranian troops, and there was no outcry from the United States, which supported Iraq at the time. In 1984, Ayatollah Khomeini secretly decided to restart the nuclear weapons program. At the time, Ayatollah Khamenei was serving as president of Iran, and he became supreme leader in 1989, when Ayatollah Khomeini died.

In 2003, probably in response to the American invasion of Iraq, which was originally justified by the Bush administration on the grounds that Iraq had weapons of mass destruction, Ayatollah Khamenei ordered a suspension of Iran’s nuclear weapons program, although he has allowed uranium enrichment efforts to continue.

At an emergency meeting of the International Atomic Energy Agency in 2005, Iran’s nuclear negotiator described how Ayatollah Khamenei had issued a fatwa declaring that “the production, stockpiling and use of nuclear weapons are all forbidden in Islam,” and noted that he had said that “Iran shall never acquire these weapons.”

In the negotiations in Istanbul, American officials seem willing to use Ayatollah Khamenei’s most recent public statements as leverage, insisting publicly, at least, that they are taking him at his word. This month, Secretary of State Hillary Rodham Clinton called on Iran to back up its assertion that acquiring nuclear weapons would be a sin.

“We are meeting with the Iranians to discuss how to translate what is a stated belief into a plan of action,” Mrs. Clinton said.

Artin Afkhami contributed research. (Copyright 2012 The New York Times Company 04/14/12)