President Hosni Mubarak is adamant he will not stand down before planned elections in September. But the US, backed by the EU, is piling on the pressure for him to go now. Friday's protests could have a decisive influence on the course of events, especially if there is violence on a large scale.

Short-term scenarios include: Climbdown: The Obama administration arm-twists Mubarak into quitting immediately and handing over power to a transitional government headed by his deputy, Omar Suleiman. That would oversee constitutional and legislative changes to pave the way for new parliamentary and presidential elections. With much talk by the regime of the need for an “honourable” solution, Mubarak is persuaded by Suleiman and the military that he needs urgent medical treatment abroad followed by a period of convalescence in distant Sharm el-Sheikh on the Red Sea. Protests subside: The Egyptian government plays the stability card, arguing that an “orderly transition” is already under way, that constitutional changes will take time, and that Mubarak's sudden departure will only make matters worse. Regime is likely to warn that the banned Muslim Brotherhood is orchestrating violence or will hijack popular protests. It may appeal to US concerns over regional issues, including respecting Egypt's peace treaty with Israel and confronting Hamas, the Palestinian Islamist group that controls Gaza. Violence escalates: Large-scale bloodshed today or on subsequent days hardens the mood in the US, which suspends or halts its annual $1.3bn in military aid to Egypt - a grave and likely game-changing blow to the position of the military. Likely to be accompanied by warnings about crimes against humanity so that continued repression carries a personal price tag for key regime figures.

Standoff: Protests continue without either serious violence or Mubarak's formal departure while dialogue between government and opposition gathers momentum and constitutional changes start to look convincing, leading to splits in an already divided and largely leaderless protest movement. The opposition has only a negative platform - that the president leave. Negotiations over a transition would be complex.— Dawn-Guardian News Service