An international agreement on Iran's nuclear programme will not alter Tehran's staunch support for the Syrian government and may even strengthen Damascus, Syria's foreign minister said Friday.

Speaking at a conference in Damascus on "confronting terrorism", Walid Muallem said those who hoped to persuade Iran to abandon Syria's government would be disappointed.

"There is a lot of talk about the Iranian nuclear agreement and its impact on the Syrian crisis," he said.

"There are those, led by the United States, who think that this agreement will enable the West to influence Iran's positions on the Syrian crisis," Muallem added, dismissing that as "delusional".

"Iran's attitudes on the crisis in Syria have not changed," the minister said.

Tehran "provided all kinds of support to the Syrian people in their struggle against terrorism before the nuclear deal, and during it, and will continue to do so after it."

In fact, he said, the agreement could end up strengthening Syria.

"Iran has entered the world stage through the widest doors, and the more powerful our ally is, the more powerful we are."

The nuclear deal between Iran and six powers led by the United States has led to speculation that broader cooperation on regional issues might now be possible.

But Iran's supreme leader Ayatollah Ali Khamenei has already insisted Tehran will continue to oppose "arrogant" US policies.

"US policies in the region differ from Iran's by 180 degrees," he said last week.

Tehran is a longstanding ally of President Bashar al-Assad's embattled government in Damascus and has remained a strong supporter throughout the uprising against him.

It has supplied money, weapons and military advisers to Assad's government.

Also Friday, Muallem thanked another key government ally, Russian President Vladimir Putin, for suggesting the creation of a new regional and international alliance to fight "terrorism."

Damascus considers all those seeking Assad's ouster "terrorists" and is not part of the US-led coalition fighting the Islamic State group with air strikes in Syria.

Muallem said it would take "a miracle" to create a new regional anti-terrorism alliance in the short-term.

"But in the medium-term, the security imperatives imposed by the reality of the spread of terrorism..., and it rebounding against its supporters, will require neighbouring countries to work with Syria to create such an alliance."

Syria accuses several of its neighbours, including Turkey and Jordan, of sponsoring "terrorism" in the country.

It dismisses the efforts of the US-led coalition, accusing its members of fomenting extremism in Syria.

Muallem made no comments about overnight air strikes carried out by Turkey on Islamic State positions in northern Syria for the first time.