The decision came a day after angry protests by the stranded Palestinians, who have complained of neglect at the hands of both the Egyptian government and the Palestinian emergency cabinet.
Hamas condemned the opening of the Karm Abu Salim crossing and said it would not allow it.

Sami Abu Zuhri, a Hamas spokesman, speaking to Al Jazeera on Monday, said: "Talking about opening Karm Abu Salim crossing targets the movement [Hamas] and all the resistance forces."
In Focus

Amr El-Kahky reports on the Palestinians stranded at Rafah

"This serves economic objectives for the Israeli occupation authorities and for some Palestinian Authority leaders."
Abu Zuhri said other solutions could be found to resolve the issue and that Hamas was willing to re-open the Rafah crossing.
Riyad al-Malki, information minister in Mahmoud Abbas' emergency government, blamed Hamas for keeping the Palestinians in Egypt.
Al-Malki and other ministers of the Fatah-aligned Palestinian president's government visited on Sunday the Palestinians who have been stranded in Egypt's Sinai Peninsula for nearly a month.
He said: "Hamas wants to keep the Palestinians suffering as long as possible and use it as a political gain."
The information minister met Palestinians in the Sinai cities of Rafah and el-Arish, telling them that they are considered "one of most important priorities of the new government", and promised that they would work to allow them to return home.
Demonstrators in el-Arish yelled at the visiting delegation, shouting slogans including: "We don't want Fatah or Hamas, we just want to get out of here."
The Rafah border terminal on the Egyptian-Gaza Strip border has been closed since June 9. Egyptian security officials estimate that 4,000 Palestinians are stranded in the Sinai.