Officials from the United Nations nuclear agency are in Tehran for talks aimed at allaying concerns that Tehran is seeking a nuclear weapon.
The visit, which began on Sunday, comes at a time of heightened tension between Iran and the West.
"We will, however, not withdraw from our nuclear rights as we have constantly acted within international regulations and in line with the laws of the non-proliferation treaty"
- Ali-Akbar Velayati, adviser to the Supreme Leader of Iran
It remains unclear whether the International Atomic Energy Agency (IAEA) team, headed by chief inspector Herman Nackaerts, would inspect nuclear sites or just discuss with Iranian officials possible military dimensions of Iran's nuclear programme.
Although not officially disclosed, the IAEA team is expected to meet with Iran's chief nuclear negotiator Saedi Jalili and atomic chief Fereydoun Abbasi.
But there will be no meeting with Ali-Akbar Salehi, Iran's foreign minister, who left Tehran earlier on Saturday to attend the African Union summit in Ethiopia.
Speaking in Ethiopia, Salehi said he was "very optimistic" about the IAEA delegation's visit.
"Their questions will be answered during this visit. We have nothing to hide and Iran has no clandestine (nuclear) activities," Salehi was quoted as saying by Iran's Mehr news agency.
"We are looking forward to start with a dialogue, a dialogue that is overdue since very long," Nackaerts said before boarding a plane in Vienna, where the UN nuclear watchdog is based.
"In particular we hope that Iran will engage with us on our concerns regarding the possible military dimensions of Iran's nuclear programme," said Nackaerts, who is heading the team along with Rafael Grossi, a top adviser to IAEA director Yukiya Amano.
Iran has said it will co-operate with the IAEA team during their three-day visit but indicated it would not give up uranium enrichment, which it considers a sovereign right.
"We have always been open with regards to our nuclear issues, and the IAEA team coming to Iran can make the necessary inspections," Ali-Akbar Velayati, adviser to Supreme Leader Ayatollah Ali Khamenei, told the ISNA news agency.
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"We will, however, not withdraw from our nuclear rights as we have constantly acted within international regulations and in line with the laws of the non-proliferation treaty," Velayati said.
If inspections are conducted, one site could be the new Fordow uranium enrichment facility south of the capital Tehran near the city of Qom, which will become operational next month.
Sources close to the IAEA said the visit would not involve inspections of nuclear facilities but would focus on resuming talks on Iran's disputed nuclear programme, which the West suspects has a military dimension.
Since 2008, Tehran has declined to fully co-operate with the IAEA but denies it is seeking a nuclear bomb.
The visit could pave the way for the resumption of talks between Iran and world powers Britain, China, France, Germany, Russia and the US. The last round of talks in January 2011 ended without a breakthrough.
Since then the EU and US have introduced a series of sanctions against Iran, including measures targeting the country's lucrative oil industry.
Mohammad Marandi, an associate professor of American Studies at Tehran University, told Al Jazeera: "If Western regimes try to strangle the Iranian people and to hurt the Iranian economy severely, then the Iranians will have no option but to punish them."
Source: Al Jazeera and agencies