"I am preparing the Israeli army for a large scale war, since it is easier to scale down to a smaller operation than to do the opposite," Lieutenant General Gabi Ashkenazi was quoted as saying in a cable from the US embassy in Tel Aviv.
The document, dated November 15, 2009, was quoted Sunday in Norwegian by Oslo-based daily Aftenposten, which said it had obtained WikiLeaks' entire cache of 251,187 leaked US embassy cables.
"The rocket threat against Israel is more serious than ever. That is why Israel is putting such emphasis on rocket defence," Ashkenazi told the US delegation led by Democrat Ike Skelton, the cable showed.
The army chief lamented that Iran has some 300 Shihab rockets that can reach Israel and stressed that the Jewish state would have only between 10 and 12 minutes warning in case of an attack. However, it was Hamas in Gaza and Hezbollah in Lebanon that posed the most acute threat, he cautioned.
According to the quoted cable, Hezbollah is thought to have more than 40,000 rockets, many of which are believed capable of reaching deep into Israel.
US officials meanwhile reportedly estimate the militant group has acquired an arsenal of around 50,000 rockets.
A 2006 war between Hezbollah and Israel killed 1,200 Lebanese, many of them civilians, and 160 Israelis, most of them soldiers. And in his comments made nearly a year after Israel on December 27, 2008 launched the deadly Gaza war, Ashkenazi said "Israel is on a collision course also with Hamas, which rules Gaza."
"Hamas will have the possibility to bombard Tel Aviv, with Israel's highest population concentration," he was quoted as saying.
The Gaza war -- a response to hundreds of rockets fired into the Jewish State -- killed some 1,400 mainly civilian Palestinians and 13 Israelis, 10 of them soldiers. It ended on January 18, 2009.
Israel had been harshly criticised for putting civilians at risk during fighting in the densely populated Gaza Strip.
However, in the cable leaked Sunday Ashkenazi is quoted saying Israel next time will not accept "any restrictions on warfare in populated areas," and insisted the army had never intentionally attacked civilian targets.