President Donald Trump destroys U.S. credibility while Iran is working toward a political solution in Syria, Iranian Foreign Minister Mohammad Zarif, said in a Twitter post on Friday.

Zarif posted the message in the midst of a trilateral meeting between Iran, Russia and Turkey focused on a looming battle against militants in Idlib province in northwest Syria.

“As @realDonaldTrump destroys U.S credibility & humiliates his ‘allies’ with “little games”, we’re delighted to engage with responsible powers today in Tehran to further move toward political solution in #Syria,” Zarif wrote.

“Agreed to work to end terrorism & avoid human suffering in #Idlib.”

Similarly, Turkish President Tayyip Erdogan, called for a ceasefire in the rebel-held region of Idlib in northwest Syria on Friday, saying said an anticipated government assault on insurgents there could result in a massacre.

But Russia’s President Vladimir Putin said Moscow opposed a truce, and Iranian leader, Hassan Rouhani, said Syria must regain control over all its territory.

The three presidents, whose countries’ are key foreign players in Syria’s long civil war, were speaking at a summit in Tehran aimed at charting a way to end the conflict.

The situation in Idlib, the insurgent’s only remaining major stronghold, is an immediate issue as President Bashar al-Assad’s forces, backed by Russia and Iran, prepare for what could be the conflict’s last decisive battle.

The UN has warned an assault could lead to a humanitarian catastrophe.

But as the leaders gathered in Tehran, Russian and government warplanes hit rebel-held parts of Idlib, the Syrian Observatory for Human Rights war monitor said.

Tehran and Moscow have helped Assad turn the course of the war against an array of opponents ranging from Western-backed rebels to Islamist militants, while Turkey is a leading opposition supporter and has troops in the country.

Their discussions in Tehran could mark a turning point in a seven-year-old war which has killed more than half a million people and forced 11 million to flee their homes.

In opening remarks, Erdogan called on Putin and Rouhani to agree to a ceasefire in Idlib, saying such an accord would be a “victory” of their summit.

However, Putin responded that he opposed a ceasefire because Nusra Front and Islamic State militants located there were not part of peace talks. Syria should regain control of all its territory, he said.

“The fact is that there are no representatives of the armed opposition here around this table. And more still, there are no representatives of Jabhat al-Nusra or ISIS or the Syrian army,” Putin said.

“I think in general the Turkish president is right. It would be good. But I can’t speak for them, and even more so can’t talk for terrorists from Jabhat al-Nusra or ISIS that they will stop shooting or stop using drones with bombs.”

Rouhani also said the battle in Syria would continue until militants are pushed out of the whole country, especially in Idlib, but he added that any military operations should avoid harming civilians.

He called on all militants in Syria to disarm and seek a peaceful end to the conflict.

The Assad government was not directly represented at the summit, nor was the U.S. or other Western powers.

Widely abhorred internationally for the brutal conduct of the war, Assad has largely reclaimed most of Syrian territory though much of it is ravaged.
As the conflict approaches its endgame, Iran, Turkey and Russia are seeking to safeguard their own interests after investing heavily militarily and diplomatically in Syria.

“The battle for Idlib is going to be the final major battle,” said Hilal Khashan, a political science professor at the American University of Beirut.

“It will be waged irrespective of civilian casualties, even though they will make an effort to minimize it.”