Egypt's Muslim Brotherhood has called for a support rally for Egyptian President Mohamed Morsi, as anti-Morsi demonstrators remained camped out at Cairo's Tahrir Square and in front of the presidential palace.

The Islamist group called for the demonstration later Wednesday outside of the presidential palace. They said the rally was called because opposition protesters were trying to “impose their opinions through force.”

Meanwhile, U.S. Secretary of State Hillary Clinton called Wednesday for an open dialogue in Egypt.

“The upheaval we are seeing now once again in the streets of Cairo and other cities indicates that dialogue is urgently needed,” Clinton said in Brussels after a two-day NATO foreign ministers meeting.

In Cairo, some of the opposition protesters there have vowed not to leave until Mr. Morsi abolishes a decree he issued last month granting him sweeping powers that place him above review from the judiciary.

On Tuesday, Egyptian riot police fired tear gas outside the presidential palace, where tens of thousands of protesters had gathered as Mr. Morsi was inside conducting business. Police tried to stop the crowd from storming the palace but soon retreated and let the marchers through a barrier and up to the palace walls. Egyptian officials say Mr. Morsi had left the palace during the march.

Many of the marchers chanted the same anti-government slogans used in the uprising that toppled former authoritarian president Hosni Mubarak.

Protest leaders called Tuesday's march a last warning to Mr. Morsi to back down from his decree. They are also against a draft constitution that the opposition says was drawn up by Islamists, without input from secularists and liberals.

A referendum on the constitution is set for December 15.