Azzam al-Ahmad, an adviser to President Mahmoud Abbas, said Wednesday that Egypt cited "special circumstances" for delaying the Rafah crossing's opening.
Egypt has kept the crossing, vital to Gaza's nearly 2 million residents, mostly shuttered since Hamas seized the territory from Abbas' Palestinian Authority in 2007.
Israel and Egypt have maintained a blockade on Gaza to isolate Hamas.
Hamas ceded control of Gaza's crossings to the Palestinian Authority under an Egypt-brokered deal last month.
The European Union, which helped monitor the crossing before the Hamas takeover, says it is sending diplomats to the region to explore "a possible redeployment" of its operation.