Olmert, and Amir Peretz, Israel's defence minister, have seen their popularity plummet after Israel failed to crush Lebanon's Hezbollah group in the 34-day war that ended in a UN-brokered ceasefire.
Olmert and Peretz, scrambling to offset a groundswell of support for their right-wing rivals, have said the war drove Iranian- and Syrian-supported Hezbollah away from the Israeli border and made way for a bolstered UN peacekeeping force.
"I know how an incumbent prime minister can become popular, there are tens of ways," Olmert said, describing himself as a "veteran political warrior" who knows how to judge his standing.
Olmert acknowledged that he might be "much more popular" today if he had heeded the calls of analysts and former generals to launch a swift ground offensive after Hezbollah captured two soldiers in a July 12 border raid.
But he said on Thursday that doing so would have endangered Israeli soldiers.
After the Hezbollah border raid, Israel at first relied on air and artillery shelling, causing a large number of Lebanese casualties but hardly denting Hezbollah's ability to fire short-range rockets into Israel.
Olmert said his falling popularity might also be arrested if he had "caved into pressure" to increase public spending and had launched a public relations campaign in response to a series of political corruption allegations.
The government-appointed Winograd commission of inquiry said its interim report will focus on the decision to go to war. It will also deal with the first five days of fighting, leaving the rest to be discussed in the committee's final conclusions.
Lieutenant-General Dan Halutz, Israel's wartime armed forces chief, has already stepped down along with two other generals.
The fighting killed 117 Israeli soldiers and 41 civilians and about 1,200 people in Lebanon, including an estimated 270 fighters from Hezbollah and other factions.