Trump sparks a firestorm after lashing out at San Juan's mayor over his handling of Puerto Rico's relief effort

In this U.S. Navy handout, sailors aboard the amphibious assault ship USS Kearsarge (LHD 3) move move pallets of supplies on the flight deck during a replenishment-at-sea with the fast combat support ship USNS Supply (T-AOE 6) for continuing operations in Puerto Rico on September 28, 2017. Kearsarge is assisting with relief efforts in the aftermath of Hurricane Maria.
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President Donald Trump issued a plea for unity on Saturday in response to the unfolding humanitarian crisis in Puerto Rico, yet critics heaped new scorn and outrage on the president after he lambasted the mayor of San Juan for her "poor leadership."

In a series of early morning posts on Twitter, Trump lashed out at Mayor Carmen Yulin Cruz, who a day earlier said officials were "killing us with the inefficiencies" in the effort to recover from Hurricane Maria.

Although she did not name Trump directly, the federal government's assistance to the island has been widely criticized, particularly after Maria laid siege to Puerto Rico's already fraying infrastructure.

Still, Trump hammered Cruz for her "poor leadership ability...and others in Puerto Rico, who are not able to get their workers to help." Trump, who said he would visit the ravaged island this week, has vowed to pull out all the stops to help the commonwealth recover, and congratulated the efforts of the military and Puerto Rico's first responders.

Later in the day, the president made an appeal for cooperation while imploring the public to dismiss what he called "fake news" that painted the government's efforts in a negative light.

Critics, however, continued to assail Trump's initial response, and rallied around Cruz and the effort to alleviate the disaster, which has left the island reeling.

We must all be united in offering assistance to everyone suffering in Puerto Rico and elsewhere in the wake of this terrible disaster.

To the people of Puerto Rico: Do not believe the #FakeNews! #PRStrong

President Donald Trump talks with reporters outside the Oval Office of the White House, September 27, 2017.
Carlos Barria | Reuters

We are with you

Puerto Rico's governor, Ricardo Rosello, said earlier this week that the administration has been responsive to the island's needs, and contrasted with Cruz's emotional plea on Friday. For most of the week, Trump has deployed Rosello's remarks to deflect criticism of the federal government's response.

Although Trump's tweets drew a measured response from Cruz herself on Saturday, they stirred a hornet's nest of criticism on social media.

The goal is one: saving lives. This is the time to show our "true colors". We cannot be distracted by anything else.

Actor Lin Manuel Miranda, who is of Puerto Rican descent and has rallied with other celebrities to contribute to the island's relief efforts, savaged Trump in a series of tweets he posted on Saturday.

'No long lines for you. Someone will say, "Right this way, sir.'

Preet Bharara, the Manhattan federal prosecutor whom Trump abruptly dismissed earlier this year, faulted the president for his own leadership failures, and mocked his response.


Charles W. Cooke, an editor for conservative journal The National Review, said that while Trump didn't deserve the early critiques of his response, his posts on Saturday had changed Cooke's opinion.

'Now he deserves everything he gets. Utterly disgraceful.'

Since Hurricane Maria slammed into Puerto Rico with gale-force winds more than a week ago, frustration has mounted amid deteriorating conditions. Power and phone connectivity is scarce, as are basic necessities on the island, which is usually a draw for vacationers from the mainland.

Drone footage from San Juan, Puerto Rico, after Hurricane Maria.

--The Associated Press and CNBC's Natalie Daher contributed to this article.