WASHINGTON (AP) — Senators of both political parties questioned Tuesday whether the White House's request for $2.5 billion is enough to prepare the United States for a possible coronavirus outbreak, even as President Donald Trump said the virus is "very well under control" here.

"If you low-ball something like this, you'll pay for it later," Sen. Richard Shelby, R-Ala., told Trump's top health official, Health and Human Services Secretary Alex Azar. The two faced each other at a budget hearing that turned into a forum for assessing U.S. readiness in the face of a rapidly evolving international health threat.

Shelby said if the virus keeps spreading, "it could be an existential threat to a lot of people in this country." He chairs the powerful Appropriations Committee, which sets spending levels for federal agencies.

Azar defended the government's response, even as Trump hours earlier sought to minimize fears about the virus spreading throughout the U.S. "We have very few people with it," the president said at a news conference near the close of his two-day visit to India.

Trump said a "lot of talent" and a "lot of brainpower" were being tapped for the response to the new coronavirus. He said the $2.5 billion request was to shore up defenses "in case something should happen" and to help other countries.

At the Senate hearing, Azar noted that nearly two months after the first alarms were raised, there's no evidence the virus has spread here beyond patients infected overseas and a few close relatives. He credited travel controls and mandatory quarantines, adding that government scientists are working to develop a vaccine and to perfect a test for detecting the virus.

"We cannot hermetically seal off the United States to a virus and we need to be realistic about that," the health chief acknowledged. "We'll have more cases in the United States, and we've been very transparent about that." If it happens, "we'll work to mitigate those."

Democratic Sen. Patty Murray of Washington said the administration's handling of the crisis has been "unacceptable."

"We cannot afford to plan on the cheap or at the last minute," she said.

"I'm deeply concerned that we are way behind the eight-ball on this," she added.

In an indication of the challenges, Azar said the government currently has stockpiled 30 million special N95 respirator masks but 300 million would be needed to protect health care workers in an outbreak.

Azar told senators that U.S. cases currently total 57. That includes 14 who either traveled to China or were close relatives of travelers; three Americans repatriated from Wuhan, the epicenter of the outbreak in China; and 40 passengers returned home from the cruise ship Diamond Princess.

The White House budget office said the $2.5 billion would be used for vaccine development, treatment and protective equipment, but Democrats immediately slammed the request as insufficient.

Coronavirus fears were credited with Monday's 1,000-plus-point drop in the Dow Jones Industrial Average, and the decline continued Tuesday.

The rapid spread of the virus around the world and its threat to the global economy has rocked financial markets, but Trump said China is getting the epidemic under control.

"They've had a rough patch and ... it looks like they're getting it under control more and more," Trump said. "They're getting it more and more under control so I think that's a problem that's going to go away, but we lost almost 1,000 points yesterday on the (stock) market."

Before the funding request, key government accounts were running low.

The White House is requesting $1.25 billion in new funding and wants to transfer $535 million more from an Ebola preparedness account — a move opposed by Democrats. The administration anticipates shifting money from other HHS accounts and other agencies to complete the $2.5 billion response plan.

Some Democrats were dismissive.

"All of the warning lights are flashing bright red. We are staring down a potential pandemic, and the administration has no plan," said Senate Minority Leader Chuck Schumer, D-N.Y.

Trump fired back in a tweet, accusing Schumer of "complaining, for publicity purposes only."

The quickly spreading virus has slammed the economy of China, where the virus originated, and caseloads are rapidly increasing in countries such as South Korea, Iran and Italy. More than 80,000 people around the world have been infected, with more than 2,500 deaths, mostly in China.

Democrats aren't the only ones complaining.

At another hearing, Acting Homeland Security Secretary Chad Wolf was pressed for answers.

Sen. John Kennedy, a Louisiana Republican, asked whether Wolf knew the projected number of cases in the U.S., among other pointed questions.

Wolf said the virus poses a "low" threat to the U.S. but couldn't provide the answers sought by Kennedy.

Appearing to grow frustrated, Kennedy said, "The American people deserve some straight answers on the coronavirus and we're not getting them."

Yet mixed messages kept coming from top White House officials.

As financial markets continued to slide Tuesday, economic adviser Larry Kudlow portrayed it as a buying opportunity for investors. "Our economy is in good shape," said Kudlow. "This virus won't last forever. We have contained it."

He added, "Long-term investors should take a good hard look at whether they want to add to their positions in the stock market."

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Lemire reported from New Delhi, India. Associated Press writers Kevin Freking, Ben Fox, Andrew Taylor, Deb Riechmann and Darlene Superville in Washington contributed.