Almost directly in line with the decline in Washington’s relations with its regional allies in Islamabad and Kabul, Tehran has intensified its diplomatic and political activity over the regional situation and Afghan issue. Iran sees the plunge in US ties with Pakistani and Afghan governments as an opportunity and is determined not to miss it. Iran’s endeavors will get a boost with the visits by Afghan President Hamid Karzai and Pakistani President Asif Ali Zardari to Tehran this week to take part in the international summit on terrorism on the request of Iran’s President Mahmoud Ahmadinejad. The summit is scheduled for 25-26 June, but Zardari will arrive Thursday on a two-day trip. Tehran’s aim is to promote regional unity with Islamabad and Kabul based on their shared interests and concerns vis-à-vis US regional plans.