WASHINGTON – President Trump defended his administration's response to the humanitarian disaster in Puerto Rico, dismissing any critics of his relief efforts as "fake news" and "politically motivated ingrates."

"We have done a great job with the almost impossible situation in Puerto Rico," Trump said. "Outside of the Fake News or politically motivated ingrates ... people are now starting to recognize the amazing work that has been done by FEMA and our great Military."

Trump's comments follow a barrage of tweets on Saturday, in which he directly targeted the mayor of San Juan, Carmen Yulin Cruz, who had questioned the pace or relief efforts to the island battered by Hurricane Maria.

While Trump accused the mayor of acting as the behest of Democrats "to be nasty to Trump," Cruz said she was only appealing for quicker help to save lives.

"I wasn't saying anything nasty about the president," Cruz told MSNBC.

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Trump is scheduled to visit the island Tuesday to review rescue efforts. He may also visit the U.S. Virgin Islands, which is also undergoing a hurricane relief effort. As Trump prepares for the trip, Puerto Rico National Guard Maj. Paul Dahlen said the president’s expected visit to the island is not affecting aid deliveries or any other relief operations.

In a third tweet on Sunday morning, Trump had kind words for Puerto Rico Gov. Ricardo Rossello, thanking him and "all of those who are working so closely with our First Responders. Fantastic job!"

Rossello told reporters Sunday that the U.S. Defense Department has increased its presence on the island, and that the emphasis remains on ensuring that “food, water and other the supplies get delivered to the people of Puerto Rico.” However, when asked whether all buildings were inspected for safety as Trump had claimed, Rossello said: "I’m not sure about that. There are areas in Puerto Rico that we haven’t gotten in contact."

Trump also drew fire on Saturday for saying some people in Puerto Rico "want everything to be done for them when it should be a community effort. 10,000 Federal workers now on Island doing a fantastic job."

FEMA Administrator Brock Long said on Fox News Sunday that relief efforts on the island represent one of the most logistically challenging undertakings the country has ever faced, particularly coming so soon on the heels of other hurricanes.

He acknowledged major challenges remain and there's still a "long way to go," but he said a lot has been accomplished.

"What I don't have patience for is the fact that what we're trying to do and what we have successfully done is we've established a joint field office in San Juan... where we're having daily conversations with all the mayors, we're working with the governor and his leadership to create unified objectives," Long said.

Long also dismissed criticism of the federal relief efforts, including from Cruz.

"We can choose to look at what the mayor spouts off or what other people spout off, but we can also choose to see what's actually being done, and that’s what I would ask."

Treasury Secretary Steven Mnuchin said Sunday that the San Juan mayor's complaints about the pace of aid were "unfair" given everything that's been done.

"When the president gets attacked, he attacks back," Mnuchin said on NBC's Meet the Press.

After getting generally high marks for his administration's handling of hurricanes Harvey and Irma, Trump has now found himself on the defensive for the preparations for Maria.

Political opponents contrasted his approach to Puerto Rico to his recent hurricane recovery efforts in Texas and Florida, for which the president spent the weekend at Camp David working on disaster response and tweeted ongoing messages of support for the damaged areas on the mainland.

Sen. Bernie Sanders, I-Vt., speaking on CNN's State of the Union, suggested skin color may be a factor in Trump's response. He also noted that Trump tweet-bombed the San Juan mayor from his "fancy golf club" in New Jersey, where he is spending the weekend, while mayor Cruz copes with a lack of food, water, and electricity.

"It is unspeakable," Sanders said. "I don't know what world Trump is living in."

Ohio Republican Gov. John Kasich, also on CNN, said "it's not appropriate" for Trump to criticize public officials who are "in the middle of a disaster."

Mick Mulvaney, Trump's director of the Office of Management and Budget, said the president is saying that, because of the island's location, the recovery project in Puerto Rico was always going to be tougher than the ones in Florida and Texas.

"This is an island that was absolutely devastated," Mulvaney said on CNN. "This was always going to be harder."

Cruz herself appeared to dismiss Trump's tweets during an interview on ABC's This Week, saying that "any dialogue that goes on just has to be able to produce results."

As for Trump's visit, Cruz said, "If he asks to meet with me, of course I will meet with him."

– Oren Dorell contributed from San Juan