At a classified meeting at the Pentagon this week to discuss U.S. policy in Iraq, two seats were reserved for foreign diplomats: the ambassadors from the United Arab Emirates and Britain.

The ambassadors were invited to a portion of the two-day meeting by John J. Hamre, the chairman of the Defense Policy Board, which advises Defense Secretary Chuck Hagel on sensitive matters and gathers to discuss top-secret information.

Hamre also serves as president and chief executive of the Center for Strategic and International Studies (CSIS), an influential Washington think tank. The Emirati and British governments are donors to the center, and the high-level meeting at the Pentagon gave the ambassadors special access to U.S. officials trying to shape the Obama administration’s policy in Iraq and elsewhere in the Middle East.

In a brief interview Wednesday as he walked out of the Pentagon after the meeting ended, Hamre said there was nothing improper or unethical about inviting CSIS donors to appear at an official, closed-door Defense Department event.

“I was asked to help the secretary of defense, through the Defense Policy Board, think about a very serious issue of national significance,” he said. “And I brought together the best people I could.”

The UAE and Britain are key players in the international coalition that the Obama administration is building against the Islamic State, the jihadist movement that has taken over large parts of Iraq and Syria. It is commonplace for diplomats to meet with U.S. government leaders to discuss policy, but it is unusual for such meetings to be arranged on an official basis by the head of a think tank that has received donations from those countries.

Navy Cmdr. Amy Derrick-Frost, a Pentagon spokeswoman, declined to comment specifically on whether it was a conflict of interest for Hamre to invite CSIS donors, but said, “every aspect of these discussions comported with the proprietary and ethical foundation this board is required to observe.”

She said the Defense Policy Board “leverages the knowledge” of foreign officials and private-sector experts, and that temporary security clearances are sometimes issued so they can attend meetings.

Also attending as an invited guest was David Ignatius, a columnist for The Washington Post. Ignatius declined to comment, saying the meeting was off the record. In an e-mail, he said he received prior approval to attend from Post Editorial Page Editor Fred Hiatt and Alan Shearer, editorial director of Washington Post News Media Services, which syndicates Ignatius’s column.

In recent years, foreign countries have played an increasingly important role in underwriting the activities of institutions such as CSIS. The donations, described in a recent New York Times article, raised concern about whether foreign governments are attempting to buy influence in Washington by shaping think-tank analysis and policy recommendations.

Think tanks are generally not required to disclose their sources of revenue, although CSIS publicly lists Britain and the UAE as donors on its Web site.

Outside the Pentagon, Hamre was reluctant to answer questions about the board, which he has led since 2007. He angrily jabbed his finger at a reporter, saying: “You’re acting like a little journalist. It’s time for you to be a real journalist.”

Later, he e-mailed a formal statement, saying it was “preposterous” to suggest that the UAE ambassador, Yousef al-Otaiba, was invited to the closed meeting because his country donates to CSIS. But he acknowledged that the participants’ overlapping roles could make for uncomfortable appearances.

“I put CSIS’s standing at risk by inviting Ambassador Otaiba to appear before a government body,” Hamre wrote. “He was asked to discuss highly sensitive and critical matters. It could have been a difficult session for him, and it would not have reflected well on CSIS. But he is by far the most knowledgeable person I could find who understands the policy thrusts in the region and the role that UAE and other states are playing in Iraq.”

UAE has become an increasingly generous donor, not only to Washington think tanks in recent years but also to other activities in the capital. It has hired lobbying firms to amplify the message that it is a strategic ally of the United States.

Otaiba said this week’s meeting was his first formal interaction with the Defense Policy Board.

“This is the first time I have spoken to the board as a group but, in my role as UAE Ambassador to the United States, I’ve had close and ongoing relationships with almost all of its members as part of the UAE-US strategic alliance,” he said in an e-mail. “Given the situation in the region today, I meet or speak with senior Pentagon and Administration officials almost every day.”

A spokesman for the British embassy confirmed Ambassador Peter Westmacott’s participation in Tuesday’s portion of the board meeting, but added “we don’t discuss the detail of the ambassador’s private meetings.”

In his statement, Hamre said he invited Westmacott because he has served as a diplomat in Iran and Turkey “and also brings a European perspective on the Middle East.”

The Defense Policy Board meets only to advise the secretary of defense and only on topics that the secretary wants, according to Hamre.

Under federal rules, advisory committees such as the Defense Policy Board are supposed to publicly advertise their meeting times and agendas at least 15 days in advance. The Defense Policy Board failed to do that for this meeting, waiting until Tuesday — the day the meeting started — to post a notice in the Federal Register.

According to the notice, the entire meeting was closed to the public because the board needed to hold “secret through top secret”-level discussions regarding Iraq and the region. The notice also stated that the Pentagon waived the 15-day requirement to publicize the meeting “due to difficulties finalizing the meeting agenda.”

Other guests included Ryan Crocker, the former ambassador to Iraq, and Zbigniew K. Brzezinski, the national security adviser in the Carter White House. Brzezinski is a trustee at CSIS and serves as co-chairman of its advisory board.

Hamre said that he invited Brzezinski “to provide a broad strategic frame of reference.” Brzezinski did not respond to an e-mail seeking comment.

Among the appointed members of the Defense Policy Board who attended the meeting were former secretary of state Madeleine K. Albright , former senator Sam Nunn (D-Ga.) and former congresswoman Jane Harman (D-Calif.), the director and president of another think tank, the Woodrow Wilson International Center for Scholars.