PARIS — France’s government welcomed Iranian President Hassan Rouhani on Thursday with promises of a new beginning in an old relationship, starting with investments to boost Iran’s flagging economy, which has been crippled by decades of sanctions.

‘‘It’s a new chapter of our relationship,’’ President Francois Hollande said in a joint news conference following a two-hour meeting with Rouhani. ‘‘I want that relationship to be useful, useful to both countries, useful to the [Middle East] region affected by wars, crises and tragedies.’’ Hollande said he raised the issue of human rights during the meeting.

France also sees the visit as a chance to draw Iran into a crisis-solving role, notably in Syria’s civil war. Iran supports the Syrian President Bashar Assad, whom Paris opposes.

‘‘We must fight terrorism’’ in Syria and Iraq, Rouhani said. ‘‘We must help the Syrian people so that the Syrian people can build a sustainable future.’’

He decried the sanctions his country was previously under, saying history has shown that they ‘‘never worked.’’ He said the nuclear deal that led to the lifting of sanctions this month can serve as a model for solutions in other crises, notably in the Middle East.

Twenty agreements were signed after Rouhani’s meeting with Hollande. Iran Air signed a deal to buy 118 aircraft from Airbus, valued at $25 billion. And PSA Peugeot Citroen announced a joint venture with Iran Khodro to produce latest-generation vehicles in Tehran by the end of 2017.

French and Iranian companies also signed agreements in the sectors of air and maritime transport, airports, health, and agriculture. The oil and gas company Total inked a deal with the National Iranian Oil Co. to purchase crude. France said the total amount of the deals signed during Rouhani’s visit could reach $32.8 billion.

Still, France has asked the European Union to consider new sanctions on Iran for its recent ballistic missile tests.