Meshaal said: "I warn and say that I see that the current situation is heading in the direction of the conditions that prevailed in the late 1990s ... that paved the way for the al-Aqsa intifada. I warn, and under 'warn' I put many red lines."
The Ezzedine al-Qassam Brigades, the armed wing of the ruling Hamas movement, broke a five-month-old Gaza ceasefire last week by firing rockets into Israel in response to the killing of nine Palestinians by Israeli forces.
Ehud Olmert, Israel's prime minister, said on Sunday that Israel would take measures to stop Palestinian fighters firing rockets from the Gaza Strip or attempting to infiltrate the Jewish state.
Meshaal defended the firing of rockets, saying it was a response to Israeli killing of Palestinians, but said he hoped that a ceasefire could be expanded from Gaza to the occupied West Bank.
Hamas formed a unity government last month with the Fatah movement of Mahmoud Abbas, the Palestinan president, in an effort to end internal fighting and ease the year-old economic embargo.
But tensions between Hamas and Fatah remain high, particularly in the Gaza Strip.
The Hamas leader, who held talks with Abbas in Cairo on Friday, has criticised Arab countries for being slow to live up to financial commitments made to the Palestinians.