Speaking to reporters during a two-day meeting of Syrian opposition groups taking place in the Saudi capital, Riyadh, Adel al-Jubeir said he hoped the various factions can come up with a common vision for Syria.
The meeting, which ends today, aims at forming a unified front ahead of proposed peace negotiations with Assad's government.
A peace plan agreed last month by 20 nations meeting in Vienna set a January 1 deadline for the start of talks between Assad's government and opposition groups.
Saudi Arabia has been a key backer of Sunni opposition blocs pushing for Assad's ouster throughout the nearly five year old Syria conflict. Among those participating in the meetings in Riyadh are hardline Saudi-backed groups such as Jaysh al-Islam and Ahrar al-Sham, who had long rejected any negotiations with Assad's government while he remained in power.
Al-Jubeir repeated Saudi Arabia's longstanding position that Syria's president must go.
"As I said before, Bashar Assad has two solutions: Leave through negotiations, which is easier and better for all. Or he will have to leave through fighting because the Syrian people refuse that this regime and person stays in power," he said.