President Obama on Thursday excoriated Congress for staying on its summer break while Zika has started to spread into the United States, and called on Americans to help him exert pressure on Congress into passing a bill to fund the fight against the virus.

"Once again, I want to urge the American people to call their members of Congress and tell them to do their job," Obama said at a press conference in the Defense Department. "Deal with this threat, help protect the American people from Zika."

"Congress needs to do its job," he said. "Fighting Zika costs money. Helping Puerto Rico deal with its Zika crisis costs money."

"Not only did the Republican-led Congress not pass our request, they worked to cut it, and then they left for summer recess without passing any new funds for the fight against Zika," Obama added.

Congress left town split on how to fund the fight against Zika. Republicans passed a bill in the House providing $1.1 billion in new funding, but Democrats in the Senate blocked it. Democrats favored a bill allowing new emergency spending that didn't have to be offset, but also opposed what they called "poison pill" riders on the GOP bill.

Republicans have said the Obama administration has not yet spent the nearly $600 million that is available, but Obama said that money is "rapidly running out."

At the same time, Obama said health experts don't expect Zika to spread in the U.S. as it has spread in Central and South America.

"I do want to be very clear, though. Our public health experts do not expect to see the kind of wide-spread outbreaks of Zika here that we've seen in Brazil or in Puerto Rico," he said.

"The kind of mosquitoes that are most likely to carry Zika are limited to certain regions of our country," Obama added. "But we cannot be complacent, because we do expect to see more Zika cases."