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US National Security Adviser H. R. McMaster speaks during a briefing in the Brady Press Briefing Room of the White House in Washington, DC, May 16, 2017.
McMaster on Tuesday denied that US President Donald Trump had caused a "lapse in national security" following reports he disclosed highly-classified information about the Islamic State group to Russian officials. / AFP PHOTO / SAUL LOEB        (Photo credit should read SAUL LOEB/AFP/Getty Images)
US National Security Adviser H. R. McMaster speaks during a briefing in the Brady Press Briefing Room of the White House in Washington, DC, May 16, 2017.
McMaster on Tuesday denied that US President Donald Trump had caused a "lapse in national security" following reports he disclosed highly-classified information about the Islamic State group to Russian officials. / AFP PHOTO / SAUL LOEB        (Photo credit should read SAUL LOEB/AFP/Getty Images)

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    McMaster facing attacks inside the White House

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McMaster facing attacks inside the White House

A source knowledgeable about the day-to-day challenges of National Security Adviser H.R. McMaster tells CNN about the difficult work environment, noting that people within the White House are trying to undermine and discredit him. CNN's Jake Tapper reports.

McMaster facing attacks inside the White House

A source knowledgeable about the day-to-day challenges of National Security Adviser H.R. McMaster tells CNN about the difficult work environment, noting that people within the White House are trying to undermine and discredit him. CNN's Jake Tapper reports.