Sanders drew a contrast between Trump and San Juan Mayor Carmen Yulín Cruz, saying Trump was "speaking from his fancy golf club, playing golf with his billionaire friends, attacking the mayor of San Juan, who is struggling to bring electricity to the island, food to the island, water to the island, gas to the island."
Sanders also said it would be fair for people to wonder if race was a factor in Trump's response to the devastation in Puerto Rico.
"Given the President's history on race, given the fact that he, a few months ago told us that there were good people on both sides when neo-Nazis were marching in Charlottesville, yeah, I think we have a right to be suspect that he is treating the people of Puerto Rico in a different way than he has treated the people of Texas or Florida," Sanders said.
Yulín Cruz said in an interview on ABC's "This Week" that White House homeland security adviser Tom Bossert called her several days ago, and the administration was coordinating with her team to provide aid. She also said she would meet with Trump if he asked her to when he visits the island on Tuesday.
Yulín Cruz maintained the focus should be foremost on saving the people of Puerto Rico.
"Let us not talk about the debt," Yulín Cruz said, referring Puerto Rico's crippling debt load. "Let us not talk about the cost of reconstruction. Let us just talk about saving lives right now."
'Judge us by the actions'
In a separate interview on the same program, White House budget director Mick Mulvaney defended Trump's tweets and said he interpreted them as Trump trying to impress upon the public how difficult the storm relief efforts were.
"I think it's unfair to say we haven't done everything we can because we have done everything that we can and will continue to do so," Mulvaney said.
"It's unfortunate that the Puerto Rico mayor wants to, excuse me the San Juan mayor, wants to sort of go against the grain," he said, adding that Yulín Cruz should visit the FEMA command center on the island.
"We'd love to have her on the team as well," he said.
Mulvaney said some people were looking for reasons to snipe at the Trump administration and that the public should consider the administration's actions over words.
"Judge us by the actions, please," Mulvaney said. "Judge us by what's happening on the island."
Puerto Rico Rep. Jenniffer González-Colón acknowledged to CNN's Ana Cabrera on Sunday that the residents of the island still needed a lot of supplies and logistics needed to improve, but the enormity of the disaster required that politics be put aside.
"This is not the time for politics, to have people from different parties blaming one another," the Republican lawmaker said. "I can tell you that the President has called me twice, actually, asking me directly how he can help, what can be improved, how many more resources or people we need. He just approved $40 million for highways, to repair highways and rebuild highways on the island. He just sent a lot of new beds for the hospitals, working with the generators, and nothing is perfect because we have been hit a catastrophic hurricane."
But Ohio Republican Gov. John Kasich, a frequent critic of the President, said in an interview on "State of the Union" that Trump's attack was uncalled for.
"It's not appropriate," Kasich said. "When people are in the middle of a disaster, you don't start trying to criticize them. I don't know what to say."