Prime Minister Benjamin Netanyahu on Sunday called on Egypt's future rulers to preserve a peace treaty with Israel after Islamists took the lead in the Arab country's first round of elections.
"We hope any future government in Egypt will recognise the importance of keeping the peace treaty with Israel in its own right and as a basis for regional security and economic stability," Netanyahu said in his first public comments on the issue since the Egyptian vote.
A first-round vote last week set Egypt's Muslim Brotherhood on course to take the most seats in the country's first freely elected parliament in six decades. The Salafi Nour Party, a more hardline Islamist group, is in second place, with a liberal bloc third.
The final outcome of the election will not be known until other parts of the country vote in two more rounds, a process that will not be complete until 11 January.
Israel has voiced concern that Muslim groups hostile to it could rise to power in the wake of "Arab Spring" revolutions that have toppled leaders in Tunisia, Egypt, Libya and Yemen.
Egypt was the first Arab country to recognise Israel, signing a peace treaty in 1979 that secured Cairo billions in annual US aid and an Israeli withdrawal from the occupied Sinai peninsula.
Sinai, which is demilitarized under the peace deal, has in recent years worried Israel as a gun-running conduit to Palestinian militants in the neighbouring Gaza Strip.
Security has frayed there further since veteran Egyptian president Hosni Mubarak was overthrown in February, prompting Israel to speed up construction of a security fence along its porous border with Egypt.
In August, eight Israelis were killed by militants who Israel said crossed into its territory from Sinai. Five Egyptian security guards were killed as Israeli soldiers pursued the gunmen.
Netanyahu said the fence, originally meant to keep out illegal African migrants, "today has security importance in light of growing instability in the Middle East" and that its construction would be sped up and completed within a year.