"Our estimate is probably more conservative than the estimates of Israeli intelligence services," Obama said in a wide-ranging interview with The Associated Press.
The president spoke to the AP on Friday, four days into the partial shutdown of the federal government. He reiterated his opposition to negotiating with House Republicans to end the shutdown or raise the nation's debt ceiling.
"There are enough votes in the House of Representatives to make sure that the government reopens today," he said. "And I'm pretty willing to bet that there are enough votes in the House of Representatives right now to make sure that the United States doesn't end up being a deadbeat."
The start of the shutdown coincided with the opening of sign-ups for the insurance exchanges at the heart of Obama's health care law. Some House Republicans are seeking changes to the law in exchange for reopening the government.
