(CNN) — President Obama sent a direct message to Iran’s supreme leader, Ayatollah Ali Khamenei, weeks before this month’s disputed election, Iranian sources said Wednesday.

The letter requested dialogue and engagement between the two nations, the sources said.

The sources said Khamenei has yet to reply to the letter but nonetheless it “had set the negotiating table in order for both sides to sit around it after the election.”

The White House refused to “get into the specifics of our different ways of communicating,” a senior Obama administration official said.

“We have indicated a willingness to talk for a long time and have sought to communicate with the Iranians in a variety of ways,” the official said.

Khamenei made an indirect reference to the letter in his sermon Friday at Tehran University.

“The U.S. president said that we were waiting for a day like this to see people on the street,” the Iranian leader said. “Some people attributed these remarks to Obama and then they write letters to say we’re ready to have ties; that we respect the Islamic republic and on the other hand they make such comments. Which one should we believe?”

One Iranian source said, “We thought President Obama would send congratulations” to President Mahmoud Ahmedinajad, and before the election, his senior advisers had already prepared a response to the anticipated note, which never came. Watch how the reported letter is part of a new policy of engagement »

The Iranian source said that the election dispute is wasting time on the issue of starting U.S.-Iranian negotiations.

“The longer it is delayed,” the source said, “the less likely it [U.S.-Iranian talks] will happen.”

Under intense scrutiny amid growing concerns over Tehran’s violent crackdown on street protests, Obama has sharpened his language on Iran.

“The United States and the international community have been appalled and outraged by the threats, beatings and imprisonments of the last few days,” Obama said Tuesday, adding that he strongly condemns “these unjust actions.”

He has not spoken in support of Ahmadinejad or his main rival, Mir Hossein Moussavi, whose supporters have taken to the streets to protest the election results that gave Ahmadinejad a second term.

Obama’s letter to Khamenei is in keeping with his publicly stated aim of engagement with Iran and his New Year’s message in which he described new way forward.

The Obama administration has “made it clear that any real dialogue — multilateral or bilateral — needed to be authoritative,” according to the senior administration official.

The official noted that the Iranians have yet to respond to a diplomatic outreach made during talks on Iran’s nuclear program on April 8. At that time, the administration asked the European Union’s international policy chief, Javier Solana, to invite Iran to new talks with the permanent members of the U.N. Security Council and Germany.

But that tack may be changing as senior administration officials in Washington told CNN that the Obama administration is seriously considering not extending further invitations to Iranian diplomats for July Fourth celebrations overseas. Some invitations already had been sent and will not be rescinded, senior administration officials said.

The officials said intense discussions on the issue were taking place, but the final decision had not been made.

The Obama administration had decided to invite Iranians to the celebrations at overseas posts as part of the president’s policy of engaging the Iranian regime.

As part of that engagement, Obama videotaped a message for the Iranian people on the Persian new year, and U.S. officials have engaged members of the Iranian government. – CNN