UNITED NATIONS —  United Nations Syria envoy Staffan de Mistura has invited Syria’s government and opposition groups for separate talks in Geneva next month in the latest bid to end the four-year-old civil war, a U.N. spokesman said on Friday.

De Mistura, who is due to brief the U.N. Security Council later on Friday, plans for “low-key” talks with each of the main stakeholders over four to six weeks in the Swiss city, Ahmad Fawzi told a news briefing.

“There will be no big meeting at the end. There will be no fanfare at the conclusion,” Fawzi said.

Major powers and regional players have been invited, but not the militant groups “Islamic State” or Jabhat al-Nusra, which are classified as “terrorist organizations”, he said. Some of those present at the talks would be able to communicate with them, he added.

Fawzi said De Mistura hoped to report back to U.N. Secretary-General Ban Ki-moon by June 30, the third anniversary of the Geneva Communiqué, a ministerial document setting out guidelines on Syria’s path to peace and a political transition.

Some diplomats have privately expressed skepticism about De Mistura’s chances of success.

But Russia has said it hopes the talks will lead to a united front against terrorism followed by a political transition.

Others have noted that separate talks on Iran’s nuclear program may also produce a deal at the end of June. A nuclear deal would ease tensions between Tehran and Washington, two of the leading powers for and against Assad, creating diplomatic momentum that could help talks on Syria.

Iran is among those invited to Geneva, according to Fawzi.