Hamas threatened on Tuesday to storm the Gaza Strip's borders in a repeat of a breach in January that allowed hundreds of thousands of Palestinians to pour into Egypt.
"All options are open to break the siege" by Israel, Khalil al-Hayya, a senior leader of the Islamist movement told a Gaza City news conference when asked if the border could be breached again.
"I expect that what will happen next will be greater than what happened before, not only against the Egyptian border, but against all the crossings," he added.
Israel has sealed off Gaza from all but vital goods since Hamas seized power there last June, in a bid to halt rocket attacks from the territory and to put pressure on the Islamist-run government.
"We call parties to move urgently and immediately to end the siege and warn of an unprecedented explosion if it continues," Hayya said.
Hamas has been negotiating with Egypt for weeks in a bid to reopen the Rafah crossing, the only gateway to Gaza that bypasses Israel.
Palestinian president Mahmoud Abbas has called for a return to a 2005 agreement in which European Union monitors were stationed at the crossing and Israel monitored it with electronic surveillance.
But Hamas, which seized power after routing forces loyal to Abbas, has rejected any foreign involvement and demanded that Rafah be reopened as an Egyptian-Palestinian crossing.
At a separate press conference Mohammed al-Hindi, a senior leader in the Islamic Jihad movement, echoed Hamas's threat.
"I told our Egyptian brothers that if the present conditions continue there will be an explosion on Egypt, and it will have to choose whether to open the crossing or open fire," he said.
On January 23, Palestinian militants demolished the border fence between Gaza and Egypt, sending hundreds of thousands of Gazans streaming into Egypt to stock up on supplies.
Egyptian and Hamas forces sealed the frontier breach on February 4.