Israel has described Egypt's decision to reopen its border with Gaza as "problematic".
The Rafah crossing, which has been closed by Egypt for the majority of the time since Hamas took over the Gaza Strip in 2007, will be now be open between 9am and 9pm except on Fridays and holidays.
According to Egypt's official Middle East News Agency, the move is aimed at "the status of the Palestinian division and [achieving] national reconciliation."
The decision comes three months after the collapse of President Hosni Mubarak's regime amid concerns that the new Egyptian leaders will not uphold the peace treaty with Israel.
Israel's deputy defence minister, Matan Vilnai, expressed reservations about Egypt's plan. He said: "It symbolises the first stage of a very problematic system for Israel."
Mark Toner, a spokesman for the US State Department, cautioned that while the move could benefit the people of Gaza, it could also pose a security risk.
Mr Toner said: "Efforts should also ensure that the transfer of weapons or other materiel and financial support for terrorism is blocked."
Hamas' foreign affairs minister Mohammed Awad said the decision reflected "the deep relation between us and Egypt".
But although the decision is of political significance, the Rafah crossing has long been circumvented by Palestinians building tunnels to smuggle weapons across the Gaza border.