President Hassan Rouhani of Iran made his debut this week at the World Economic Forum in Davos, Switzerland, where he expanded on his government’s charm offensive by wooing investors and reassuring political leaders of his determination to complete a comprehensive nuclear deal with the major powers. But his benign image and deft political skills could not erase or excuse the ugly fact that Iran remains the main ally of Syria’s president, Bashar al-Assad, in the destruction of Syria and its people.

Mr. Rouhani, who took office in August, is eager to fulfill his promises of improving Iran’s relations with the world and reviving an economy devastated by international sanctions and his predecessor’s mismanagement. He quickly reached an interim deal with the major powers that curbs significant aspects of Iran’s nuclear program.

When the deal took effect on Monday, United Nations inspectors confirmed that Iran had begun suspending most advanced uranium-fuel enrichment and taken other agreed-upon steps. In exchange, Iran received what the United States called “limited, targeted and reversible sanctions relief for a six-month period.” At Davos, Mr. Rouhani clearly was looking to speed the day when all sanctions are lifted and Iran can achieve the economic growth and international acceptance that has been lost since the 1979 Islamic revolution. At a meeting with top oil executives, he and his oil minister promised to have a new, attractive investment model for oil contracts by September that could help win back business from Western interests.

For now, it is essential that broad sanctions, including restrictions on Iran’s access to the international financial system, remain in place until a comprehensive nuclear agreement is reached. The United States insists that they will remain in place, though it may not be easy to prevent an erosion of the penalties. Investors are eager to jump back into the Iranian market, as are many governments.