Washington: US President Barack Obama sent a secret letter to Iran`s Supreme Leader Ayatollah Ali Khamenei last month stressing the two countries` shared interest in fighting Islamic State militants in Iraq and Syria, a media report on Thursday said.

According to the Wall Street Journal, the letter in mid-October said cooperation between the United States and Iran on combating the militant group was tied to a deal being reached between Iran and other nations on its nuclear program.

The newspaper cited people briefed on the letter. It said Obama administration officials declined to discuss the letter with the Journal.

"Administration officials didn’t deny the letter’s existence when questioned by foreign diplomats in recent days," it said.