Washington (CNN) President Donald Trump issued a firm denunciation of political violence in announcing the arrest of the mail bomb suspect Friday , but repeatedly undercut his attempts to come across as a unifying leader at a time of crisis.

On camera during an unrelated White House event, Trump condemned the serial bomb mailings as "terrorizing acts."

But on Twitter and later in off-the-cuff remarks that reflected the polarizing nature of his presidency, Trump appeared to downplay the gravity of the case that saw suspect devices sent to two ex-presidents and a list of his top Democratic critics.

And on a conspiratorial note, he complained that media coverage of the mailings was drowning out Republican momentum heading into the elections in 11 days.

It was the latest sign of the President's reluctance to put politics aside to fulfill expectations many Americans have for the role of the President at a time of national anxiety. He goes through the motions but undercuts his own calls for unity with political jabs.

White House officials repeatedly criticize the media for not giving his statements of condemnation sufficient coverage. But they are frequently diluted by more politically divisive swipes that raise questions about the President's sincerity.

'We must never allow political violence to take root'

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Trump appeared in the East Room of the White House before a pumped up crowd of black conservative leaders, shortly after the arrest of 56-year-old Cesar Sayoc in Florida in connection with the suspect packages. The bombs were mailed to targets including former President Barack Obama, to the home of former Secretary of State Hillary Clinton and President Bill Clinton, billionaire liberal donor George Soros, and the CNN bureau in New York.

"These terrorizing acts are despicable and have no place in our country," Trump said, while also praising law enforcement officials for the swift arrest, since the first packages started arriving on Tuesday.

"We must never allow political violence to take root in America," he said. "I'm committed to doing everything in my power as President to stop it."

Trump's remarks, read from a teleprompter were in keeping with a grave moment, and would stand comparison to any comments by a previous President at a time when Americans were worried about their security.

But Trump has no intention of calling those targeted with pipe bombs, a senior White House official told CNN.

And he declined to mention any of the targets or their party affiliation by name, only citing them as public figures, adding to indications that the President rejects any suggestion that his own rhetoric could be partly to blame for fostering a febrile political atmosphere in which the packages were sent. He also noted a media organization had received a bomb, but did not specify that it was CNN.

"But the bottom line is that Americans must unify, and we must show the world that we are united together in peace and love and harmony as fellow American citizens," Trump said at the White House. "There is no country like our country, and every day we are showing the world just how truly great we are."

His unifying and elevated tone contrasted sharply with his attitude towards the case when he was not reading a script.

Earlier, in a tweet, the President appeared to give credence to conservative media narratives that the media's focus on the bomb mailings was deliberately designed to hurt GOP prospects at the polls in 11 days time.

"Republicans are doing so well in early voting, and at the polls, and now this "Bomb" stuff happens and the momentum greatly slows - news not talking politics. Very unfortunate, what is going on. Republicans, go out and vote!" Trump tweeted.

Political messaging

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Trump has made repeated attempts to frame the closing days of the election around an inflammatory message about immigration and a caravan of migrants from Central America that is slowly moving towards the US in Mexico and is currently around 1,000 miles from the border.

But his political strategy was upended by blanket media coverage of the fallout from the suspect devices, more of which were being discovered on Friday,

His tweet, and the use of quotation marks around the word "bomb" raised questions about whether he already knows that the devices were not meant to go off, -- information that is not yet public -- and if he is using that knowledge to shape the political aftermath of the episode and to downplay the widespread public angst stirred by whoever sent the packages.

White House spokesman Sarah Sanders earlier said that the President was being briefed constantly on latest developments in the case.

Later in his event at the White House, Trump attacked what he termed "fake polls" and members of the crowd gathered in the East Room responded with exclamations of "fake news" and "CNN sucks."

He also aired a fresh complaint that his political initiatives leading into the midterms are being blanked out by coverage of the suspect packages.

Trump said there was a "big, big" announcement on Thursday on reducing drug prices but "it didn't get the kind of coverage it should have because it was a big thing."

"But ... we're competing with this story that took place that now -- our law enforcement's done such a good job -- so maybe that can start to disappear rapidly because we don't like those stories."