President Mohamed Mursi offered opponents a say in amending Egypt's constitution, but railed against "enemies" he accused of undermining the new democracy in a defiant speech ahead of mass protests planned to demand that he step down.

As the Muslim Brotherhood head of state ended a marathon televised address early on Thursday, liberals said they had heard nothing new, including any offer to include them in committees to draft institutional reforms and study "national reconciliation".

Opposition plans to stage a huge protest on Sunday, when Mursi completes a year as Egypt's first freely elected leader, were unchanged. After two people were killed in factional street fighting on Wednesday, the risk remains of a violent showdown, as Islamists also plan to rally in force.

Instability in the biggest Arab nation could send shocks well beyond its borders. It has long been an ally of the United States, which still funds Egypt's armed forces heavily.

The army, for decades the arbiter of Egyptian politics, has warned it may step back in to keep order. The head of the armed forces had a front-row seat in the audience for Mursi's speech in Cairo, which lasted nearly three hours.

General Abdel Fattah al-Sisi, who was promoted by Mursi, has warned feuding politicians that if they fail to forge consensus and violence runs out of control, then troops would intervene.

Mursi offered a diagnosis of Egypt's problems since the revolution of 2011 that, with military help, forced out Hosni Mubarak. "Political polarization and conflict has reached a stage that threatens our nascent democratic experience and threatens to put the whole nation in a state of paralysis and chaos," he said.

He acknowledged unspecified "errors" and promised reforms to help Egypt's fast-growing young population; he spoke of cutting unemployment and raising the minimum wage but blamed opponents for the instability that has driven the economy into crisis.

But unmoved liberal opponents mocked the length of his speech, his personal attacks on public figures and the cheering of the partisan audience seen on national television.

From Reuters