Tehran officials go to Damascus over pilgrims affair, and reach out to Turkey, Lebanon and Qatar in diplomatic offensive

Iran has launched a new campaign to intervene in the Syrian crisis, sending its top officials across the Middle East, blasting US "warmongering" and publicly backing a defiant Bashar al-Assad as the country sinks deeper into war.

Saeed Jalili, Iran's powerful national security adviser, met the Syrian president in Damascus on Tuesday, while Iran's foreign minister urged Turkey and Qatar to use their influence with Syrian rebels to free 48 kidnapped Iranian pilgrims.

Iran said that it was holding the US responsible for the fate of the pilgrims, three of whom were reported killed in shelling on Monday. Anti-Assad fighters have claimed the pilgrims are in fact Iranian Revolutionary Guards helping suppress the 17-month long uprising.

The message was passed to Switzerland, which represents US interests in Iran. "Because of the US manifest support of terrorist groups and the dispatch of weapons to Syria, the US is responsible for the lives of the 48 Iranian pilgrims abducted in Damascus," it said.

Jalili pledged that Iran would not allow anything to break the "axis of resistance" of which Syria formed a "fundamental element," Syria's ad-Dounia TV reported. The phrase usually also includes Hezbollah in Lebanon and the Palestinian group Hamas, united by hostility to Israel.

Assad told Jalili of "the determination of the people and government of Syria to cleanse the country of terrorists," the TV station added. Syria, said Assad, was "capable of thwarting the foreign conspiracies".

Iran's burst of diplomatic activity appeared designed to take advantage of the collapse of efforts by Kofi Annan, the UN envoy on Syria, though most anti-Assad rebels, like the western and Arab countries that back them, see Iran as part of the problem and incapable of providing a solution.

"The Iranians are everywhere," said one western diplomat. "It's hard to know whether they are just concerned by the pilgrim issue — if they are pilgrims —or if this a wider drive to be be proactive and avoid being isolated by the Sunni Arabs."

Syrian TV broadcast pictures of the Assad-Jalili meeting — the first shown of the president since 22 July, when he appointed a defence minister to replace one of four security chiefs assassinated by the Free Syrian Army (FSA). Jalili also met Ali Mamluk, Assad's security adviser.

In Tehran meanwhile, Ali Larijani, the speaker of the Iranian parliament, attacked US "warmongering" and warned that its "malevolence in Syria will consume Israel". Israel has threatened to strike Iran's nuclear programme to preserve its own nuclear monopoly.

On Thursday, Tehran is due to host a conference for countries it says have realistic positions on Syria. Lebanon declined the invitation but six other Arab countries are said to have accepted, along with Pakistan, Venezuela, India and Kazakhstan, as well as Russia and China, which have vetoed any UN security council action on the crisis.

Next week Iran's President Mahmoud Ahmadinejad is attending a summit of the Organisation of the Islamic Conference in Mecca — potentially putting him on a collision course with Saudi Arabia's King Abdullah, a key supporter of the Syrian opposition. Iran was conspicuously excluded from June's talks in Geneva on the Syrian crisis convened by Annan at the insistence of the US, Britain and the EU, which are at odds with Tehran over its nuclear ambitions and Middle East policies.

Iran said that its foreign minister, Ali Akbar Salehi, would ask Turkey's Ahmet Davutoglu to intervene over the pilgrims affair and "to warn and remind the Ankara government of its responsbilities". Turkey, Saudi Arabia and Qatar were all told to stop helping "the warmongering policies of the US in Syria," in the words of the Iranian army chief of staff, Major General Seyed Hassan Firouzabadi.

Jalil, visiting Lebanon on Monday, said: "We believe that Syria's friends must help to totally stop the violence, organise national dialogue and general elections in this country, and send humanitarian aid for the Syrian population." Lebanon's former prime minister, Saad Hariri, said Jalili was not welcome in Beirut at a time of mass killings by Assad.

Iran has always denied allegations that it is providing military assistance to Assad but the Syrian opposition, western governments and Israel all insist it has at minimum sent advisers on security and communications. Iran is said to have passed on expertise it honed in crushing the protests that followed the disputed presidential elections in 2009.

Politically Tehran has stood behind Assad while putting out feelers to some Syrian opposition groups. The two countries have had a close alliance since the 1979 Islamic revolution in Iran.

In another regional move, Iran sent its vice-president, Hamid Baqai, to Cairo to invite the new Egyptian president, Mohamed Morsi, to attend the non-aligned summit in Tehran. Iranian-Egyptian relations have been strained for years and remain a highly sensitive issue.

Larijani made clear that Iran blamed the US, not Assad, for the situation in Syria. "The fire that you [the US] ignite in the Levant will swallow the terrified Zionists," he told MPs. "Kofi Annan's resignation and US contacts with certain politicians in the region and military support for the Syrian rebels that is meant to throw Syria into chaos shows there is a new plan by international criminals."