"Common borderlines between the two countries have not changed since 1639 and this is a unique example in the world," Gul

Iran's President Mahmoud Ahmadinejad officially welcomed his visiting Turkish counterpart Abdullah Gul who is on a four-day official visit.

The two leaders have begun private talks at the Presidential Office. During the ceremony held in Tehran on Monday, the national anthems of the two countries were played and the two presidents reviewed a guard of honor, IRNA reported.

President Gul arrived in Tehran on Sunday at the head of a high-ranking 135-member delegation upon an invitation of his Iranian counterpart. The Turkish president was received by Iranian Foreign Minister Ali Akbar Salehi at Mehrabad International Airport upon his arrival.

Senior Iranian and Turkish officials are to discuss a whole range of topics, including mutual relations and regional and international developments.

Gul is also slated to visit the Iranian cities of Esfahan and Tabriz during his trip.

On the eve of his Tehran visit on Saturday, the Turkish president told IRNA that he would be accompanied by a host of Turkish investors and businessmen during the trip.

The Iran-Turkey Joint Economic Cooperation Commission is also planned to be formed during the trip, he added. He described Iran and Turkey as two regional heavyweights, which "treat each other with mutual respect."

"Common borderlines between the two countries have not changed since 1639 and this is a unique example in the world," Gul went on to say. Referring to the recent developments in Egypt, Gul said the region is undergoing a significant change, a Press TV correspondent reported. “The Middle East is going through an immense period of comprehensive structural change, which was never witnessed before,” he said.