Upon his arrival Straw met his Iranian counterpart Kamal Kharrazi.
The two-day visit is within the framework of continuous contacts between the two countries.
Straw will also meet President Khatami and discuss bilateral, regional and international issues. Tehran's visit will be the first leg of his visit to four Middle Eastern countries.
The trip is Straw's fourth to the Islamic Republic in less than two years, but first in the post-Iraq war era.
Contrary to Iran-U.S. ties, Tehran-London relations have improved despite all their ups and downs.
Though Blair firmly backed U.S. President George W. Bush over Iraq, he has preferred a more conciliatory approach towards Iran.
However, Straw's visit will be a tough one, for only last week British Prime Minister Tony Blair supported a student unrest in Iran which the Iranian officials condemned as interference in their internal affairs.
Britain's ambassador to Tehran was summoned to the foreign ministry to hear Iranian complaints over those comments.
Straw will be therefore asked to give acceptable explanation about Blair's comments.
The British in past indirectly colonized Iran by getting fabulous oil concessions. London helped the U.S. in toppling the popular government of Mohammd Mossadeq in 1953, for he hand nationalized the oil industries. But those memories were fading away with the improvement ties. Blair spoiled the game. Straw is expected to mend fences.
Straw last traveled to Iran in October 2002, when the US-led war to oust Saddam Hussein from power in Iraq was looking increasingly imminent. Then he sought to secure a minimum of Iranian cooperation with the coalition forces, and that request is expected to be made again amid mounting security problems for U.S. and British troops in Iraq.
The Supreme Assembly for Islamic Revolution in Iraq led by Ayatollah Muhammad Baqir al-Hakim was based in Tehran before the collapse of Saddam Hussein. Majority of the Iraqis like Iranians are shias. Iran enjoys spiritual and political influence among the Iraqis and influential Iraqi political groups, but has not interfered in Iraqi internal affairs.
Diplomats told the AFP Sunday that Straw would be asking Iran to use its influence with Iraqi Shia Muslim groups to play a "more constructive" role in the post-war reconstruction effort.
"For us to leave Iraq as quickly as possible, we need as much cooperation as we can get," a British Foreign Office source said.
"Otherwise we get bogged down and have to stay longer. Neither Iran nor Britain wants that, so we are hoping Iran can give some of the Shiite groups a nudge in the right direction."
Straw may discuss Iran's nuclear programs with the Iranian officials. The issue featured during Russian President Vladimir Putin's talks in London with British Prime Minister Tony Blair last week. Moscow is a prime supplier to Tehran's nuclear program.
Straw is expected to encourage Iran to unconditionally sign an additional protocol to the nuclear Non-Proliferation Treaty (NPT), which would allow surprise International Atomic Energy Agency (IAEA) inspections of suspect facilities.
Iran argues that it is ready to sign the additional protocol provided the sanctions are lifted and other NPT members fulfill their commitments in transferring nuclear technology to Iran for its nuclear program which is under the supervision of the IAEA and is merely for peaceful purposes.
Russia has said that it would continue its cooperation with Iran even if Iran decided not to sign the NPT's additional protocol.
Iran's nuclear programs are merely for peaceful purposes. The Chief of the IAEA told the CNN last month that "Iran's nuclear program is not weapons program."
SM/SM
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MNA