Mr. Bush also announced steps to ease environmental standards governing fuel grades.
The moves came as political pressure intensified on Mr. Bush to do something about gasoline prices that are expected to stay high throughout the summer.
Mr. Bush said the nation's strategic petroleum reserve had enough fuel to guard against any major supply disruption over the next few months. The reserve holds 685 million barrels, available in an emergency.
"So, by deferring deposits until the fall, we'll leave a little more oil on the market. Every little bit helps," he said.
Wholesale gasoline futures prices for June delivery dropped 8 cents a gallon to $2.10 on the New York Mercantile Exchange immediately upon Mr. Bush's remarks.
Easing the environment rules will allow refiners greater flexibility in providing oil supplies since they will not have to use certain additives such as ethanol to meet clean air standards. The suspension of oil purchases for the federal emergency oil reserve is likely to have only modest impact since relative little extra oil will be involved.
Today's speech comes in response to angry voters who are beginning to blame both the war in Iraq and the rising price of gas on the administration, CBS News correspondent Bill Plante reports.
The high cost at the pump has turned into a major political issue, with Democrats and Republicans blaming each other for a problem that is largely out of Congress' control, CBS News correspondent Sharyl Attkisson reports. Republicans are hoping that they can do enough in the short term that the voters won't remember the high gas prices in November, Plante says, but Democrats want to make sure voters don't forget.