Iranian Foreign Minister Ali Akbar Salehi is traveling to Turkey for previously unscheduled talks that are expected to focus on the conflict in Syria and the abduction of dozens of Iranians there.
The Iranian Embassy said Salehi will meet Turkish Foreign Minister Ahmet Davutoglu in Ankara on August 7.
Syrian rebels who are fighting against President Bashar al-Assad's regime abducted 48 Iranians outside Damascus on August 4.
Iranian authorities say those abducted were pilgrims visiting a Shi'ite shrine but the rebels said they were members of Iran's Revolutionary Guards in Syria on a "reconnaissance mission."
A Syrian rebel spokesman said on August 6 that three of the Iranians had been killed in a government air strike.
Salehi has asked his Turkish and Qatari counterparts to help secure the release of the captives.
Iran is a close Syria ally, while Turkey has been one of the strongest critics of Syrian President Assad's response to the 17-month uprising against his rule.
Iran's official media said the Iranian foreign ministry summoned the Swiss ambassador to Tehran late on August 6 over the kidnapping of the Iranians in Syria.
Switzerland represents the diplomatic interests of the United States in Iran as the two countries have no diplomatic relations.
The Iranian foreign ministry told the Swiss envoy that because of U.S. support for the Syrian rebels, Iran would hold the United States responsible for the lives of the kidnapped Iranians.
On August 7, Assad met with the secretary of Iran's National Security Council, Saeed Jalili, who flew to Damascus after ending a visit to Beirut.
Following the talks, Jalili told an Iranian TV channel that Iran held governments providing aid to Syrian rebels responsible for the abduction of the Iranian nationals in Syria.
Assad's 'Days Are Numbered'
In what is seen as another bid to secure the release of the abducted Iranians, the secretary of Iran's National Security Council, Saeed Jalili, flew to Damascus on August 7 after ending a visit to Beirut.
Meanwhile, the United States has said that the recent defection of Syrian Prime Minister Riyad Hijab shows the Syrian regime is "crumbling from within."
Hijab is the most senior Syrian official to have defected so far. He was appointed to the post two months ago. On August 6, White House spokesman Jay Carney maintained that his defection demonstrated that Assad's "days are numbered."
"That the titular head of the Syrian government has rejected the ongoing slaughter being carried out at Assad's direction only reinforces [the impression] that the Assad regime is crumbling from within," he said.
A spokesman for Hijab said the former prime minister is joining the rebels in protest at the "genocide" committed by Assad's forces.
Hijab's whereabouts have not been officially confirmed, but he is reported to have defected to Jordan heading to Qatar.
Syrian state media meanwhile said government troops pressed on with their onslaught on rebel-held areas in the northern city of Allepo on August 7, reportedly killing at least 25 rebels.
WHO Warns Of Severe Drugs Shortages
In related news, the World Health Organization (WHO) says Syria is facing severe shortages of medicines for treating chronic diseases and a rising number of casualties as the conflict between government troops and rebels fighting against President Bashar al-Assad's regime continues.
"The impact of this situation, of course, is devastating for people who need drugs on a daily basis," said WHO spokesman Tarik Jasarevic. "[This is affecting] people with chronic conditions, people with mental health situations, and also for people who are on antibiotics to prevent infections when being treated for conflict-related injuries."
The UN agency said drugs for tuberculosis, hypertension, diabetes and cancer were urgently needed, as well as hemodialysis for kidney diseases.
It said many drug-makers have closed down, and health facilities have stopped functioning.
Azeri Embassy Suspends Operations
Elsewhere, Azerbaijan's foreign ministry has announced that the country’s embassy has officially suspended its operations in Syria due to security reasons.
According to the ministry, 60 citizens of Azerbaijan as well as Azerbaijan's Ambassador and the Embassy personnel have left Syria and there are no Azerbaijani citizens in the country at the moment.
The ministry officials also expressed their hope that the situation in Syria would stabilize in the nearest future and that the embassy would resume its operations in Damascus.
With reporting by AFP, AP, Reuters, ITAR-TASS, and Interfax