Israel's top general has warned that the military will have to invade the Palestinian enclave again if militants keep firing rockets into the Jewish state.

If a new offensive against the coastal territory is launched, military officers say it will likely be more destructive than Israel's widely condemned 22-day invasion in December 2008.

Any move against Gaza, ruled by Hamas militants since 2007, will incense Egypt, where Islamist parties have scored major gains in parliamentary elections and are likely to dominate the next government.

Israel fears the Islamists' rising power following the toppling of Egyptian President Hosni Mubarak in February will threaten its landmark 1979 peace treaty with its western neighbor.

Israel commanders are debating military moves to counter a future threat across the Sinai Desert, the key battleground in four Middle Eastern wars between 1948 and 1973.

Chief of Staff Lt. Gen. Benny Gantz marked Tuesday's anniversary of the 2008 invasion, Operation Cast Lead, by warning that although that "excellent operation" forced Hamas to curtail its attacks, the deterrence factor is eroding.

A new large-scale invasion is looming, he said, and it would be "swift and painful … I do not advise Hamas to test our mettle …

"I believe the state of Israel cannot continue to live under the active threat of Hamas in the Gaza Strip. Sooner or later, there will be no escape from conducting a significant operation."

Up to 20,000 Israeli troops were involved in Cast Lead, which was preceded by several days of heavy airstrikes. Palestinian casualties were 1,417 killed, half of them civilians. Israeli fatalities were 13 soldiers and three civilians killed.

Israel was heavily censured internationally for the invasion with allegations of war crimes by the troops. It denied the charges.

The Israelis have carried out two airstrikes on Gaza this week, with militants linked to al-Qaida as the main targets. The attacks followed reports that the Israeli air force has hit two truck convoys carrying Gaza-bound arms shipments in Sudan.

Sudanese news outlets said the long-range airstrikes took place over the last month. Similar strikes were carried out in 2009 against arms consignments reportedly sent by Iran.

Events in Egypt, where the emergence of long-banned Islamist parties is likely to threaten the 1979 peace treaty with Israel, are causing deep concern among Israelis who for 30 years have demilitarized their southwestern border.

The military hasn't engaged in desert warfare since the 1973 war and no senior officers have experience in waging large-scale tank operations that are the hallmark of that kind of warfare.

The Egyptian military has apparently lost control of the vast Sinai Peninsula, where jihadists linked to al-Qaida have infiltrated heavily and recruited fighters among disgruntled Bedouin tribes long-neglected by Cairo.

Eight Israelis were killed in a major raid by militants in August, heightening tension along the 280-mile border.

But Israel's main fear is that eventually the peace treaty, which bans large Egyptian forces in Sinai, will be amended or scrapped. The treaty has formed the core of Israel's security and foreign policy since 1979.

If it is discarded, the country's geopolitical strategy will collapse, heightening the possibility of renewed hostilities in a region bracing for war between Israel and Iran that is likely to engulf the entire Middle East.

While Mubarak was a staunch supporter of the U.S.-brokered treaty with Israel, most of Egypt's 82 million people oppose it and support the Palestinians.

The Jerusalem Post's military correspondent, Yaakov Katz, reported Thursday that Israel's military is examining two scenarios involving Egyptian forces in Sinai.

"The first involves an Egyptian decision to deploy troops for training," Katz wrote. "The second sees the movement of an Egyptian division pinto the peninsula, on the sidelines of a future war Hezbollah or Syria, as a demonstration of unity with the Arab countries."

As a result, the military's Planning Directorate "has recommended that a Muslim Brotherhood victory in the ingoing Egyptian elections serve as the cutoff line for when the military should begin establishing long-lead items -- such as new divisions and combat squadrons," Katz noted.

When Gantz took over as chief of staff in February, he recommended implementation of an immediate procurement plan aimed at establishing new military formations.