Donald Trump's Secret Service protection had been increased prior to assassination attempt due to Iran threat: Sources

The U.S. Secret Service in recent weeks had increased Donald Trump's security detail due to intelligence indicating there was an Iranian threat to assassinate the former president, according to three officials familiar with the matter.

There is no indication the plot was related to the assassination attempt against the former president on Saturday.

The sources have suggested Iran has been making these types of threats since the assassination of Iranian military officer Qasem Soleimani in January 2020.

CNN was first to report the increased detail.

"These accusations are baseless and biased," according to the representation of Iran in the United States. "From the perspective of the Islamic Republic of Iran, Trump is a criminal who should be tried and punished in court for ordering the assassination of General Soleimani."

It added, "Iran has chosen the legal path to hold him accountable."

The U.S. has been taking these threats seriously by providing protection to both former Secretary of State Mike Pompeo and former national security adviser John Bolton.

Threats emanating from Iran against Trump and his senior administration officials after the military strike that killed Soleimani never subsided, but intelligence gathered in recent months indicates the Iranian regime may have become more intensely focused on carrying out a plot against Trump, according to an administration official, who reiterated there is no known connection between Iran or any of its proxies and Thomas Matthew Crooks, the alleged shooter at Saturday's rally in Butler, Pennsylvania.

"The Secret Service and other agencies are constantly receiving new potential threat information and taking action to adjust resources, as needed," said Secret Service Chief of Communication Anthony Guglielmi. "We cannot comment on any specific threat stream other than to say that the Secret Service takes threats seriously and responds accordingly."

National Security Council spokesperson Adrienne Watson said Tuesday they have "been tracking Iranian threats against former Trump administration officials for years, dating back to the last administration," and that the threats stem from Iran seeking revenge for Solemani's assassination.

"We consider this a national and homeland security matter of the highest priority," she said in a statement.

ABC News' Justin Ryan Gomez contributed to this report.