The United Nations envoy to Syria said on Friday he will begin meeting in May with the country's government, opposition groups, and regional powers including Iran to assess by the end of June whether there is any hope brokering an end to the war.Staffan de Mistura briefed the UN Security Council on the latest bid to find a political solution to the 4-year conflict that has killed some 220,000 people, displaced an estimated 7.6 million and forced nearly 4 million to flee the country.UN Secretary-General Ban Ki-moon asked de Mistura earlier this month to "focus much more to re-launch a political process" after his attempt to broker a local truce in the northern city of Aleppo failed to materialize."There is nothing new telling us today that the political process will succeed or not," de Mistura told reporters. "We will start in early May and we will be meeting one after the other, everyone. Not together, separately.""By the end of June we should hopefully be in the position of reassessing whether there is any convergence on issues of substance or not," de Mistura said, adding that he will report his findings to Ban.He said Iran would be invited as it was a major player in the region and had influence in Syria. Ban withdrew a last minute invitation to Iran to Syria peace talks in January last year after the Syrian opposition threatened to boycott."The UN and myself have the right and will be inviting everyone, including Iran," de Mistura said.Other key world powers would also be consulted, but not the militant groups Islamic State or Nusra Front, which are classified as "terrorist organizations," UN spokesman Ahmad Fawzi said earlier on Friday in Geneva. Some of those present at the talks would be able to communicate with them, he added.De Mistura described his planned meetings as "a stress test of the willingness to narrow the gaps" three years after the agreement of the Geneva Communique, a document setting out guidelines on Syria's path to peace and a political transition."There is no excuse for us to wait," he said. "The immensity of the human suffering ... obliges us to seek out even the remotest possibility for some type of change."Some diplomats have privately expressed skepticism about De Mistura's chances of success.But Syrian ally Russia has said it hopes the talks will lead to a united front against Islamic State, an al-Qaida offshoot that has seized large swathes of Syria and neighboring Iraq, followed by a political transition.