WASHINGTON — The Iranian diplomat released Tuesday preceding the announcement that Iran would free the 15 British sailors it had taken hostage was being held in a joint Iraqi and American facility, and was released in part because of a decision at the highest levels of the American government.

The decision to release Jalal Sharafi on Tuesday was made at the White House, according to an administration official who asked to be anonymous because of the sensitivity of the information. The release took place over the objections of some commanders in the field. Mr. Sharafi, the second secretary of the Iranian Embassy in Baghdad, is believed by American military intelligence also to be a member of the lethal Quds Force, the terrorist-supporting organization whose members have been fair game for American soldiers and Iraqi allies since a change in the rules of engagement was issued in December.

The origins of Mr. Sharafi’s detention and the decision to release him shed new light on the high-stakes diplomacy between Britain and Iran over the fate of the British sailors. Both Prime Minister Blair and President Bush yesterday welcomed the decision to release the 15 royal marines, whose confessions were broadcast on Iranian television. While there was speculation in both the American and British press that Mr. Bush’s remarks earlier this week referring to the sailors as “hostages” had caused a breach in the American-British relationship, the new information suggests the two English-speaking allies had been coordinating closely throughout the crisis.

The release of Iranian nationals detained by America was one of the primary Iranian demands during the negotiations. “They think they won this round. They were able to take the hostages and suffer no consequences,” an American official said.

At the same time, many Iranians remain in American custody, including the five men alleged to be members of the Quds Force. They were captured January 10 during a raid of an Iranian outpost in Irbil. Yesterday, Iran’s press reported that Washington had agreed to allow emissaries from Tehran to visit the five Iranians being held. Prime Minister Maliki has also called for their release.

Pentagon and White House spokesmen on Tuesday and Wednesday insisted publicly that the release of Mr. Sharafi was solely an Iraqi decision. Indeed, when Mr. Sharafi was kidnapped in February, Pentagon spokesman said that his abduction was not the work of any members of multi-national forces in Iraq. The Iranians, through diplomatic channels, formally accused America of having ordered the abduction.

The administration official yesterday said that Mr. Sharafi’s capture was not ordered by American forces, but he was interrogated in a facility overseen by both Iraqi and American commanders.

“Had this guy been in Iraqi custody, we all know he would have been in Iran weeks ago,” an Iraqi diplomat said yesterday on condition of anonymity.

Speculation on the terms of the release of the 15 sailors made its way all the way to the White House yesterday. In an interview with ABC radio, Vice President Cheney said he did not know if the sailors had been released because of a quid pro quo arrangement.

He did, however, warn of giving into the demands of hostage takers. “Once people start taking hostages or kidnapping folks on the high seas and then are rewarded for it by getting some kind of political concession or some other thing of value, that would be unfortunate,” he said.

An adviser to the National Security Council and the State Department in the Reagan administration, Michael Ledeen, who himself was an interlocutor with the Iranians when America secretly sold arms to free Americans taken by Iran’s proxies, Hezbollah, said yesterday, “There is always a quid pro quo, we don’t know yet what it was.”

Not all Iran watchers, however, believe that Iran got the best of the exchange yesterday. The deputy director of the Washington Institute for Near East Policy, Patrick Clawson, said yesterday, “I don’t think the British gave them anything.”

Mr. Clawson said, “The Iranians got very little for this. They managed to persuade the Americans that they are the same people who took the hostages in 1979. They managed to persuade the Europeans that Iranians are a bit wild and unpredictable. They managed to persuade Arabs that Iran has continuing claims on Arab territory. They managed to persuade their own people that the revolutionary activity is placed above practical activity. This episode did not gain much sympathy for Ahmadinejad from Persian nationalists and it cost him in his international image.”