Saudi Arabian Foreign Minister Adel al Jubeir has rejected Russia’s offer to help Syria's Assad regime fight against ISIS.
Juber spoke on Tuesday in New York after meeting with Saudi allies and said Bashar al Assad must give up power or be turfed out by force.
The Saudi foreign minister also called on other countries to boost support to Syrian opposition to topple Assad or be faced with having to take the "military option."
He also criticised Iran's support for Assad, depicting Tehran as an "occupying power" in Syria and blaming it for instigating terrorism and radicalism in the region.
"There is no future for Assad in Syria, with all due respect to the Russians or anyone else," Jubeir told reporters in New York.
He pointed out just two conceivable results for a settlement in Syria, saying a transitional chamber coming to power through a political process would be the "preferred option."
Juber giving no details for the second option that includes military option "could be a more lengthy process and a more destructive process, but the choice is entirely that of Bashar al-Assad."
"Whatever we may or may not do we're not talking about," adding "There is a Free Syrian Army that is fighting against Bashar al-Assad.”
He also noted that the Syrian moderate opposition is fighting the Assad regime and is supported by many countries.
"And we expect that this support will continue and intensify," he said.
The foreign minister said the best solution for Assad is the Geneva I agreement formula that was decided at a peace conference in 2012.
The Geneva I agreement includes specifies the need for a “transitional government body with full executive powers" which lays the groundwork for a transitional government.
"And, sometime between the formation of this council and elections -– whether it's a day or a week or a month, I don't know -– President Assad would sail into the sunset," he said.
However, Iranian President Hassan Rouhani and Russian President Vladimir Putin earlier this week called on attendees during the 70th session of the United Nations General Assembly at the UN Headquarters in New York to support Assad to help defeat ISIS.
Putin proposed a Security Council resolution to govern foreign military action in Syria, but Saudi Arabia - one of the main participants in the existing US-led coalition against ISIS - rejected this.
"I think if the Russians were serious about fighting DAESH, they could join the existing international coalition," said Jubeir, using the Arabic acronym for the group.
"But for them to go out and insert forces into Syria... is a big step, and is an indication that their objective may be to prop up the Assad regime more than it is to fight DAESH."
Jubeir denied that the European powers are “going soft” and deferring to Russia to solve the problems in Syria.
"Iran is part of the problem and cannot be part of the solution," adding "It should withdraw its forces from Syria and withdraw the Shiite militias that it inserted into Syria and then it can talk about a diplomatic solution," Jubeir declared.
When asked whether Russia and Iran might support a transition away from Assad's rule, he admitted: "Hope is not that great."