CAIRO — Egyptian opposition leaders, facing dire warnings from the military about the country’s growing chaos, banded together Wednesday for the first time and pressed President Mohammed Morsi to form a national unity government as a way to halt the violence that has led to dozens of deaths in the past week.

But even as secular and Islamist groups crossed an ideological divide to try to find a way out of the spiraling violence, Morsi rejected the idea during a visit to Germany, where he said a new government would only be formed after parliamentary elections in April.