Cooper Allen, and Gregory Korte

USA TODAY

The federal government is censoring 37 pages of emails from Hillary Clinton's private email server, saying they contain information considered "top secret." The move marks the first time her State Department emails have been accorded such a high level of classification and comes just days before the Iowa caucuses.

Seven email chains are being withheld in their entirety from a release scheduled later Friday for including "top secret" information.

"The documents are being upgraded at the request of the intelligence community, because they contain a category of top secret information," State Department spokesman John Kirby said. He added, though, that the messages had not been designated as top secret when they were sent, though the department "is focusing on whether they need to be classified today." .

Clinton, who served as secretary of State from 2009 to 2013, has long maintained that she did not send or received information that was classified at the time, which Kirby said Friday was the case.

She's in a tight battle with Vermont Sen. Bernie Sanders in Iowa, which holds caucuses that open the 2016 primary calendar on Monday.

After the department's announcement, Clinton press secretary Brian Fallon said in a statement that the campaign objected to the decision.

"We firmly oppose the complete blocking of the release of these emails," Fallon said. "Since first providing her emails to the State Department more than one year ago, Hillary Clinton has urged that they be made available to the public. We feel no differently today."

The State Department has been releasing monthly batches of Clinton's emails following a court order last summer. News coverage of most releases have largely highlighted quirky office routines and humorous requests and responses from Clinton, but Friday's announcement triggered criticism from her GOP rivals about her decision to use a private email server, which has hung over her presidential campaign from its start.

GOP front-runner Donald Trump chimed in on Twitter that this latest release was "a disaster" for Clinton. "At a minimum, how can someone with such bad judgement be our next president?"

When he retweeted the news, Jeb Bush said the country needed a president who could be trusted: "Obviously that's not @Hillary Clinton."

Republican National Committee Chairman Reince Priebus tweeted Friday that "Clinton has removed all doubt that she cannot be trusted with the presidency."

For his part, Sanders on Friday stuck to previous statements about Clinton's emails, saying that the situation shouldn't be politicized.

"The voters of Iowa and this nation deserve a serious discussion of the issues facing them," he said in a statement.

Earlier this month it was announced that the State Department asked for a one-month extension to produce all of Clinton's emails, which critics suggested was politically motivated to come after the opening primaries.

"It's clear that the State Department's delay is all about ensuring any further damaging developments in Hillary Clinton's email scandal are revealed only after the votes are counted in the early nominating states," Priebus said at the time.

White House Press Secretary Josh Earnest defended the delay in releasing all of Clinton’s emails on Friday.

“I can tell you with full confidence that there is — has been no political interference in this process,” he said. “I think the extraordinary request that Secretary Clinton put forward to actually release her emails is something that, I'm not sure has a precedent, at least for federal office holders.”

He also said he doubted many Iowa Democrats were particularly interested in Clinton’s emails.

“In the context of a presidential campaign, people are going to have a whole bunch of reasons to criticize any of the candidates,” he said. “So it's not surprising to me that there are certain political opponents of Secretary Clinton that are looking for a way to use this situation to criticize her. That is part of the process. And she and her team, I'm confident, will muster a robust defense.”

The department also announced that 18 emails between Clinton and President Obama would also be withheld from Friday's release. Kirby said the department's decision to not include messages between Clinton and the president had been "widely covered months ago."