(AP) -- President Barack Obama said Tuesday that the United States can't be seen as shying away from battle against Ebola and must support health care workers who are returning from the front lines in Africa.

Obama did not directly criticize quarantine policies for returning health care workers implemented in New York and New Jersey, but he said monitoring of those who come back from the fight needs to prudent and "based in science."

"We don't want to discourage our health care workers from going to the front lines and dealing with this in an effective way," he said.

Obama said a robust response in Africa will stop the spread of the disease in the United States. He reminded Americans only two people have contracted the disease in the U.S. and both are now disease-free.

The president spoke to reporters from the White House after a phone call with one of those patients, nurse Amber Vinson, just after her release from the hospital. He also called a USAID team deployed to West Africa and said he plans to meet Wednesday with public health workers who have there or are planning to go to talk about how public policy "can support the incredible heroism that they are showing."

"America cannot look like it is shying away because other people are watching what we do," Obama said. "If we don't have robust international response in West Africa, then we are actually endangering ourselves here back home. In order to do that, we've got to make sure that those workers who are willing and able and dedicated to go over there in a really tough job, that they're applauded, thanked and supported. That should be our priority. And we can make sure that when they come back they are being monitored in a prudent fashion."

A hodgepodge of state policies, some of which directly contradict Obama's recommendations, has sowed confusion about what's needed to stop Ebola from spreading in the United States. While public health advocates denounce state quarantines as draconian and scientifically baseless, anxious citizens in non-quarantine states are asking whether they're at greater risk because their governors and the president have adopted a lesser level of caution.

For the first time, the CDC on Monday recommended 21 days of isolation and travel restrictions for people at highest risk for Ebola -- a nurse stuck by a needle while treating an Ebola patient in Guinea, for example -- even if they have no symptoms. States are still free to go above and beyond the CDC guidelines.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Disease at the National Institutes of Health, defended the Washington policy Tuesday, but said that states have a right "to go the extra mile" if they wish.

In an appearance on ABC's "Good Morning America," Fauci declined to criticize the more stringent quarantine policies implemented in New York and New Jersey by Govs. Andrew Cuomo and Chris Christie. "'They're doing it in good faith."

Christie said Tuesday he feels the CDC's latest guidance is "incredibly confusing."

"The CDC is behind on this," he said on NBC's "Today" show. "Governors ultimately have responsibility to protect the public health of people within their borders."

An order issued Friday by New Jersey, like one in New York, requires three-week quarantines for anyone who treated Ebola patients in West Africa -- not just those deemed high-risk because of a needle-stick or failure to use proper protective gear. But under the new federal guidelines, those lower-risk workers merely must have their temperatures monitored twice a day.

Legal experts say New York and New Jersey could be on shaky legal ground. To justify infringing on an individual's civil liberties, like freedom of movement, states face a high bar to prove their orders are based on science and epidemiology. Courts also like to see that states are acting as narrowly as possible rather than in broad strokes, such as lumping together everyone who treated Ebola patients even if they're healthy.

"We have not seen for decades and decades the state or federal government say a whole category is going to be subjected to quarantines," said David Fidler, who teaches international and public health law at Indiana University.

In fact, such broad quarantines are almost unheard of in U.S. history. Almost always, they have been limited to diseases that are airborne and easy to catch. Public health experts say Ebola is neither.

When an influenza pandemic dubbed the "Spanish Flu" infected millions in 1918, major U.S. cities closed schools and imposed strict quarantines. New York considered quarantining tuberculosis patients in the 1990s, and isolated some who wouldn't comply with treatment.

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Reach Josh Lederman at http://twitter.com/joshledermanAP