The package would reportedly amount to more than $30bn (£14.8bn) over the next 10 years.
Washington is reportedly preparing a package of major arms sales to Saudi Arabia and other Gulf states because of concerns over Iran's nuclear programme.
US defence aid to Israel currently stands at $2.4bn a year - the new package would amount to a 25% increase.
Mr Olmert said the aid had been agreed at a meeting with US President George W Bush in Washington last month.
Saudi arms deal
The BBC's Bethany Bell in Jerusalem says the package is seen as an attempt to allay Israeli concerns over the planned arms deal with Saudi Arabia, reportedly worth $20bn (£9.8bn) over the next decade.
Defence officials quoted by US media said the sales would include advanced weaponry, missile guidance systems, upgraded fighter jets and naval ships.
Mr Olmert said the increased support was a sign of US commitment to maintain Israel's military "advantage over the Arab states".
"We understand the need of the US to assist the moderate Arab states which are in one front with the US and us in the fight against Iran, and on the other hand we appreciate the renewed and re-emphasised support for Israel's military and security advantage," he said.
© 2007 BBC News