The European Union leaders Herman Van Rompuy and Jose Manuel Barroso have given warning to Egypt's army and interim government that the bloc was ready to "review" ties failing an end to violence and return to dialogue.
In a statement released on Sunday, the presidents of the European Council and European Commission said that further escalation could have "unpredictable consequences" for Egypt and the region.
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"The calls for democracy and fundamental freedoms from the Egyptian population cannot be disregarded, much less washed away in blood," Van Rompuy and Barroso said.
"In co-operation with its international and regional partners, the EU will remain firmly engaged in efforts to promote an end to violence, resumption of political dialogue and return to a democratic process.
"To this effect, together with its member states, the EU will urgently review in the coming days its relations with Egypt and adopt measures aimed at pursuing these goals."
The statement was released 24 hours before senior diplomats from the 28 EU nations hold emergency talks on Egypt in Brussels in which they are expected to call for a snap meeting of foreign ministers within the next days.
Saying it was crucial that violence end immediately, the statement added that "while all should exert maximum restraint, we underline the particular responsibility of the interim authorities and of the army in bringing clashes
to a halt.
"The violence and the killings of these last days cannot be justified nor condoned. Human rights must be respected and upheld. Political prisoners should be released."