The top Democrat on the Senate Intelligence Committee,
"I don't think the approach is sufficient to the job," Feinstein, of California, said on CBS' "Face the Nation."
FOR THE RECORD:
A previous version of this article said Feinstein spoke on CBS' "Meet the Press." She spoke on CBS' "Face the Nation."
"It's enormously strong and it has to be dealt with in a very strong manner," she said of Islamic State, also known as ISIS or ISIL. "This has gone on too long now and it has not gotten better, it's gotten worse."
Feinstein, who has complained since last year that President Obama has been too cautious in dealing with Islamic State, did not offer details on a more aggressive approach beyond saying the approximately 50 U.S. special operations troops being sent to work as advisors with Kurdish militias and other rebel groups in northern Syria were not enough.
"I think we need a specific, larger special operations plan," she said. "One group of 50 is fine for what they're doing so far, but it's not going to solve the problem."
The Obama administration's tactics to defeat Islamic State have come under fire in the wake of the Paris terrorist strikes. Friday's attack on a hotel in the capital of Mali by militants linked to Al Qaeda added to the concerns.
"If you want to track down, kill and defeat ISIS, if you only have a containment strategy within Iraq and Syria, you really don't understand the problem because North Africa is full of ISIS fighters," Nunes said on CNN's "State of the Union."
"The president, to have a successful strategy, is going to [have to] admit that they've got it wrong and they need to re-look at a larger strategy that deals with North Africa, the Middle East, all the way over to Afghanistan [and] Pakistan," Nunes said.
About 65% of registered voters said Obama hasn't been aggressive enough in fighting Islamic State, according to a Fox News poll released Sunday.
At a news conference in Malaysia on Sunday, Obama said the coalition of about 65 countries that the U.S. has organized to fight Islamic State "will not relent" and was "intensifying our strategy on all fronts."
"We will not accept the idea that terrorist assaults on restaurants and theaters and hotels are the new normal -- or that we are powerless to stop them," Obama said at the end of a three-nation tour to attend economic and regional summits. He vowed that "destroying ISIL is not only a realistic goal, we're going to get it done."
Brett McGurk, the administration's special envoy to the coalition fighting Islamic State, said the effort was making progress.
In the last two weeks, operations in Syria and Iraq cut off a main supply route to the Syrian city of Raqqa, the militants' de facto capital, he said on "Face the Nation."
Those strikes helped "set the conditions to accelerate" the fight, McGurk said. The 50 special operations forces will "be going in very soon" to northern Syria, he said.
"We're going to pressure them and strangle them in the core, and that means all around Iraq and Syria," he said of the extremists. "As we suffocate and strangle them in the core, we're also going to work to strangle their international networks."
But Feinstein said the administration needed to be more aggressive because "we don't have years" to defeat Islamic State.
"There may be some land held by ISIL in Iraq and Syria that has been taken back, but for all of that there's much more they have gained in other countries," she said.