Former New York City mayor Rudy Giuliani challenged former CIA Director John Brennan over his threat to pursue legal action against President Donald Trump over the revocation of his security clearance.

"You’re not a blowhard?"

Giuliani, who is on the president's personal legal team, tweeted his taunt Monday from his official social media account.

"Today President Trump granted our request (Jay Sekulow and me) to handle your case," Giuliani said in a tweet addressed to Brennan.

"After threatening if you don’t it would be just like Obama’s red lines," he added. "Come on John you’re not a blowhard?"

Giuliani was referring to the failure by former President Barack Obama to follow up on his warning in 2013 to Syrian leader Bashar al-Assad that using chemical weapons would constitute a "red line" for the United States. Later, when Assad was accused of using those weapons, Obama did nothing to enforce the "red line."

Brennan had told Rachel Maddow on MSNBC that he was seeking the possibilities for legal action against Trump over the revocation of his clearance privileges.

"I think as you can imagine, a number of lawyers have reached out to say that there is a very strong case here, not so much to reclaim [my security clearance] but to prevent this from happening in the future."

"And so, I am thinking about what it is that I might want to do. At this time, I'm trying to make sure that the principle is what is going to be defended and supported, and this is something that should be repeated."

"The worst CIA Director in our country’s history"

President Trump also taunted Brennan from his social media account Monday.

"I hope John Brennan, the worst CIA Director in our country’s history, brings a lawsuit," the president tweeted.

"It will then be very easy to get all of his records, texts, emails and documents to show not only the poor job he did, but how he was involved with the Mueller Rigged Witch Hunt," he added. "He won’t sue!"

"I challenge Maxine Waters to say impeachment!”

Giuliani similarly taunted another vocal critic of the president, Rep. Maxine Waters (D-Calif.), in May when she said she was going to keep pushing for Trump's impeachment.

“You don’t hear them say the words impeachment anymore, I challenge Maxine Waters to say impeachment!” he told Fox News' Sean Hannity.

“Say it, say impeachment, sweetheart, just say it!” he added.