By John Irish

TEHRAN (Reuters) – France vowed on Monday to act as defender of Iran’s nuclear deal, which U.S. President Donald Trump has threatened to tear up, but said it was imperative Tehran abide strictly by the conditions of the accord.

Arriving in the Iranian capital for a two-day visit, French Foreign Minister Jean-Marc Ayrault said it was in the “common interest” that the 2015 accord under which Tehran agreed to curb its nuclear program in return for lifted sanctions was obeyed.

During the U.S. election race Trump had branded it “the worst deal ever negotiated”, telling voters he would either rip it up or seek a better agreement.

“I’m coming as the defender of the accord, but to be vigilant and explain that they (the Iranians) must be irreproachable,” Jean-Marc Ayrault told reporters after landing in Tehran.

“We harbor real concerns about the U.S. administration’s attitude towards this agreement,” he said.

The deal was brokered by the United States, Russia, China, Britain, Germany and France. Paris took one of the hardest lines against Tehran in the negotiations, but has been quick to restore trade ties.

Major French corporations including planemaker Airbus, oil major Total and automobile manufacturers Peugeot and Renault have all signed deals.

Ayrault said that while Tehran had “largely” kept to the terms of the deal, it had pushed the spirit of the accord over the past year by carrying out several ballistic missile tests.

“We want this agreement to be respected. It is in the common interest of the international community that it is,” Ayrault said.

The foreign minister is due to meet Iranian President Hassan Rouhani, Foreign Minister Mohammad Javad Zarif and the powerful Secretary of Supreme National Security Council, Ali Shamkhani.

The visit, which includes an economic conference where some contracts may be concluded, will provide an opportunity for talks on Syria. Paris is a vociferous opponent of Iran’s backing of Syria’s leader, Bashar al-Assad.

“We will discuss our disagreements, notably on Syria. “We had hoped Iran would be less aggressive in the region,” Ayrault said, referring to the period since the nuclear deal.

On Sunday, Trump spoke by telephone with Saudi Arabia’s King Salman, a close U.S.-ally in the Middle East. A White House statement said the two leaders agreed on the need to address “Iran’s destabilizing regional activities.”

(Editing by Ingrid Melander and Richard Lough)