WASHINGTON (AP) — Secretary of State John Kerry urged the Syrian opposition on Thursday to attend next week’s peace conference in Switzerland and said any individual chosen to lead a political transition in the war-torn country must be acceptable to both the government and opposing forces.

The opposition groups, which will vote Friday whether to attend the peace conference, say it should lead to a transitional government that would see Syrian President Bashar Assad step down and end four decades of his family’s rule in Syria. The government rejects the demand and says Assad may run for re-election.