The United States and Iran have been holding held secret direct talks for at least half a year on the sidelines of the world powers' central negotiations in Geneva, which led to a deal early Sunday.

The details of the secret channel were revealed early Sunday morning by blogger Laura Rozen on the Al-Monitor website, citing a senior U.S. official involved in the back channels.

The covert talks were led by U.S. Deputy Secretary of State William Burns, according to Rozen, who has been closely covering the nuclear negotiations over the past few years and is considered one of the leading sources of information on the matter in the American media.

While Rozen's report indicated that the initial meeting between the two sides was held just prior to the Iranian presidential election, the Associated Press reported later Sunday morning that the secret channel was established as far back as March 2013.

Five separate meetings were been held over the course of the last nine month between the American and Iranian officials, according to AP. One of these meetings was held before the Iranian election, and the other four took place after Hassan Rohani had been elected president.

Most of the meetings were held in the Gulf state of Oman, and were kept secret from most of the U.S.' allies including Israel.

Senior Israeli government officials had claimed in press briefings over the last two months that the Americans were holding secret direct talks with Iran, but did not reveal details regarding the identities of the individuals involved in the talks, nor was it clear then where the information had come from.

The Israelis said during these briefings that the negotiations between Iran and the world powers in Geneva were in fact a cover-up for the real talks being conducted between Tehran and the United States.

According to AP, .S. President Barack Obama informed Prime Minister Benjamin Netanyahu of the secret channel two months ago during a meeting at the White House. The U.S. updated the world powers of the existence of the secret channel only after updating Israel, AP said.

It is not yet clear whether Israel had prior knowledge of the secret channel from intelligence sources.

Obama told Netanyahu only about two of the meetings with the Iranians, which took place after Rohani's election, and made no mention of the first set of talks held in March. This was part of the promise made by the Americans to Iran, according to AP.

A day after Obama updated Netanyahu, the Israeli premier delivered a harsh address lambasting Iran at the UN General Assembly.

Other news sources on Sunday confirmed Rozen's report, citing senior American officials. "We had some limited bilateral discussions with the Iranians in addition to the P5+1 negotiations that were aimed at developing ideas that we could provide in the P5+1 negotiations," Reuters quoted a U.S. official as saying.

According to Rozen's report, Washington used the initial meeting before the Iranian election to put out feelers to see whether Tehran would be interested in entering serious nuclear negotiations following the election.

Rohani's election and his declarations immediately after clarified to the Americans that the chance for real negotiations with Iran was much greater than in the past. Burns was in touch with senior officials in the Iranian foreign ministry, who were close associates of his counterpart Mohammad Javad Zarif and of Rohani.

The U.S. officials quoted in Rozen's report did not name the Iranians who took party in the secret talks, but Al-Monitor said the description of them indicated that they could include Deputy Foreign Minister Abbas Araghchi and Deputy Foreign Minister Majid Ravanchi.

In addition to Burns, the U.S. officials involved in the talks included Jake Sullivan, Vice President Joe Biden's national security adviser, Puneet Talwar, the National Security Staff senior director for Iran, Iraq, and Persian Gulf affairs.

Burns organized an exchange of letters between U.S. President Barack Obama and then-Iranian President-elect Rohani in August, according to Rozen's report. Burns then met with senior Iranian officials in order to prepare for possible meetings between the parties on the sidelines of the United Nations General Assembly in September. These contacts led to a half-an-hour meeting between U.S. Secretary of State John Kerry and his Iranian counterpart, Zarif, and then to a telephone conversation between Obama and Rohani.

The back channel was so secret that some representatives of the world powers involved in the nuclear negotiations with Iran had no idea, while others were informed of the matter only in the last few weeks.

Burns even traveled to Geneva during the second round of nuclear talks, a few weeks ago, and again last week, for the current negotiations. He stayed in a separate hotel and did not make an appearance at the Intercontinental, where the official talks were taking place. Senior Iranian officials and the members of the American negotiating teams skipped out on the formal talks a few times to meet with Burns.

Some of the points comprising the interim agreement reached between Iran and the six powers were based on these secret talks between the U.S. and Tehran, integrated by the Americans into the official document.