VIENNA, Austria —  China, an opponent of harsh U.N. Security Council sanctions against Iran, has nonetheless recently provided the International Atomic Energy Agency with intelligence linked to Tehran's alleged attempts to make nuclear arms, diplomats have told The Associated Press.

Beijing, along with Moscow, has acted as a brake within the council, consistently watering down a U.S.-led push to impose severe penalties on Tehran for its nuclear defiance since the first set of sanctions was passed in late 2006.

A Chinese decision to provide information for use in the agency's attempts to probe Iran's purported nuclear weapons program would appear to reflect growing international unease about how honest the Islamic republic has been in denying it ever tried to make such arms.

The new development was revealed by two senior diplomats who closely follow the IAEA probe of Iran's nuclear program. One commented late last week and the other Wednesday.

The IAEA declined comment, and nobody was picking up phones at the Iranian and Chinese missions to the IAEA.

John Bolton, the previous U.S. ambassador to the United Nations and before that the U.S. undersecretary of state in charge of the Iran nuclear dossier, said any such Chinese move would be "potentially significant" because of Beijing's former military ties to Tehran.

In a telephone call from Washington, Bolton said America believed that the Chinese had helped Iran develop its nuclear program, particularly in one area of uranium enrichment, "plus they had cooperation on ballistic missile programs as well."

The diplomats said Beijing was the most surprising entry among a fairly substantial list of nations recently forwarding information to the agency that adds to previously provided intelligence, and which could be relevant in attempts to probe Iran for past or present nuclear weapons research.

But they said several other countries not normally considered to be in the anti-Iran camp had also done so in recent weeks.

The diplomats — who demanded anonymity because their information was confidential — declined to name individual nations. But they attributed a generally increased flow of information to the U.N. nuclear watchdog to concerns sparked by a multimedia presentation to the 35 IAEA board members by the agency in February about intelligence previously forwarded by member states on Iran's alleged clandestine nuclear arms program.

One of the diplomats said the agency also was on the lookout for misleading information provided it, either inadvertently or in attempts to falsely implicate Iran.

One example, he said was a document showing experiments with implosion technology that can be used to detonate a nuclear device. While the document appeared genuine, it was unclear whether it originated from Iran, said the diplomat.

Suspected weapons-related work outlined in the February presentation and IAEA reports preceding it include:

—uranium conversion linked to high explosives testing and designs of a missile re-entry vehicle, all apparently interconnected through involvement of officials and institutions;

—procurement of so-called "dual use" equipment and experiments that also could be used in both civilian and military nuclear programs; and

—Iran's possession of a 15-page document outlining how to form uranium metal into the shape of a warhead.

A U.S. intelligence estimate late last year said Tehran worked on nuclear weapons programs until 2003, while Israel and other nations say such work continued past that date.

Tehran continues uranium enrichment, which can generate the fissile core of nuclear warheads, and has led to three sets of Security Council sanctions but insists it is developing the technology only for its other use — power generation.

It denies ever trying to make atomic arms and last month declared the issue of its purported nuclear weapons strivings — and any attempt to investigate them — closed, asserting that information suggesting it ever had a nascent nuclear arms program is fabricated.

But the agency has signaled it is not giving up on its efforts to investigate purported military aspects of Tehran's nuclear activities. Other diplomats told the AP that deputy director general Olli Heinonen planned to meet in the next few days with Ali-Ashgar Soltanieh, Iran's chief delegate to the agency, to press for answers.

Ahead of that tentative meeting, Gregory L. Schulte, the chief U.S. delegate to the IAEA, urged Tehran to end its stonewalling. He told the AP that with the next IAEA report due in about two months, time was running out for Iran to "explain these serious indications of troubling activities."

An IAEA report in February said suspicions about most past Iranian nuclear activities had eased or been laid to rest. But it also noted that Iran had rejected the information provided by IAEA member nations to the agency for its probe of suspected weapons research as false and irrelevant.

It also noted that Iran had blocked agency requests to talk to key officials suspected of possible involvement in past military nuclear programs, among them one identified by diplomats as nuclear engineer Mohsen Fakhrizadeh.

They told the AP that he and others active as academics in Iran's civilian nuclear faculties are suspected by the agency of key roles in secret nuclear activities with a possible military dimension, including the procurement of "dual use" equipment.

In a summary recently forwarded to the AP, the National Council of Resistance of Iran, an opposition group that claims to have informants inside the Iranian government, identified three others as Revolutionary Guard commander Fereydoon Abbasi, Seyed Jaber Safdari and Mohammed Mehdi Nejad-Nouri.

It said the three and others are involved in clandestine nuclear weapons-related research at three Iranian universities: Beheshti; Malek Ahstar and Imam Hossein.

Asked for verification, a senior diplomat of an IAEA member state said that a fact check run by his country's relevant agency showed the claims to be generally accurate. Another senior diplomat also said the information appeared to be fairly reliable.