Russian President Vladimir Putin was in Tehran on Wednesday for a day of meetings with his Iranian and Azerbaijani counterparts.

After meeting with Iran's Supreme Leader Ayatollah Ali Khamenei, President Hassan Rouhani and Azerbaijani President Ilham Aliyev, Putin expressed strong support for the Iran nuclear deal.

"We oppose any unilateral change in the multilateral nuclear deal," Putin said according to a statement from the supreme leader's office. "We oppose linking Iran's nuclear program with other issues including defensive issues."

Praising Putin's "strong" character, Khamenei said it was "possible to have logical dialogue and cooperation with Russia as a big power about big jobs that require determination and effort."

"Iranian and Russian cooperation has had a great impact in fighting terrorism in the region," Rouhani said, according to a statement from his office. "The joint cooperation and consultations are very important in the final stages too."

The talks between Azerbaijan, Iran and Russia largely focused on improving road and rail links to the neighboring countries on the Caspian Sea.

Read more: Doing business with Iran: no easy choice

Fight against IS winding down

"We are very pleased that, apart from our bilateral relations, our two countries play an important role in securing peace and stability in the region," Iranian President Hassan Rouhani told Putin during his opening remarks for the official visit.

With the fight against the "Islamic State" (IS) militant group winding down after US-backed forces liberated Raqqa, international attention has shifted once again to a political solution for Syria's nearly seven-year conflict.

Read more: 'Islamic State': Will it survive a post-caliphate future?

Both Tehran and Moscow back Syrian President Bashar al-Assad and coordinate trilateral de-escalation talks with Turkey in the Kazakh capital of Astana. Even the UN's chief negotiator Staffan de Mistura has described a "moment of truth" for the peace process after IS' defeat.

'Sanctions pressure'

Last month, US President Donald Trump refused to certify a nuclear deal that has curbed Iran's nuclear program in exchange for the international community dropping sanctions. He also announced new sanctions against Iran's elite Revolutionary Guard, accusing it of "supporting terrorism."

"Today sanctions are a tool Washington resorts to in the first place. That means, by and large, the substantial degradation of the basic principles of foreign policy," said Russia's Deputy Foreign Minister Sergey Ryabkov, according to the state-run news agency TASS.

"Perhaps, that's the object. The US has always been 'famous' for its ability to pursue the policy of controlled crises and teeter on the brink of crises escalating into a hot phase."

ls/jm(Reuters, dpa)