Roger Stone, a long-time Trump friend and former political adviser, told the Post: "He's not going to take an attack by James Comey lying down.
"Trump is a fighter, he's a brawler and he's the best counterpuncher in American politics."
Meanwhile Alan Dershowitz, a Harvard Law School professor and criminal law expert said it's hard to tell a very wealthy and powerful man not to tweet.
It comes as several Republicans have also urged the President to turn off the TV and phone.
Senate Intelligence Committee Chairman Richard Burr, a Republican from North Carolina, who will chair the Comey hearing said Trump tweeting won't change the testimony.
According to CNN, many Republicans fear Trump's tweeting could add to the spectacle surrounding the testimony.
Senator Jeff Flake of Arizona said there had been speculation the President would live tweet.
"I would argue that's not a good idea. I think anybody would tell him that," he said.
But Kansas Senator Pat Roberts went one step further, urging the President to say nothing at all.
"You never get hurt by what you don't say ... or tweet," he said.
While Trump's tweeting is all part of his brand, Republicans fear posting today is not appropriate and critics could use it to argue he's trying to influence things.
IMPEACHMENT CALLS GROW
The saga comes as two House Democrats announced they will be launching a longshot bid to impeach Trump.
The effort by Al Green of Texas and Brad Sherman of California has little chance of success in the Republican-led House and doesn't even have the backing of many fellow Democrats, the Associated Press reported.
Despite that, the politicians said they were drafting articles of impeachment because Mr Trump obstructed justice when he fired Comey.
Federal authorities said they had definitive evidence the Kremlin meddled in the US presidential election.
"The question really is whether the President can obstruct justice with impunity," Green said.
"We live in a country where no congressmen, no senator and not even the President of the United States of America is above the law."
Green first called for Trump to be impeached in a speech last month.
Neither politician would give a definitive timeline on when they plan to file the articles of impeachment but Sherman said it could happen in weeks, not months.
He also acknowledged any vote in the House to impeach Mr Trump would fail - unless further evidence of possible wrongdoing comes to light.
Many Democrats have distanced themselves from impeachment talk, pending the outcome of the investigation.
In a stinging opinion peace for the Washington Post, blogger Paul Waldman wrote the Russia scandal was not Watergate yet but it was certainly getting a lot closer to it.
While admitting the scandal was "feeling awfully familiar" to Richard Nixon and the Watergate scandal, Waldman wrote he didn't believe the President would be impeached - at least as long the Republicans control the House.
"To paraphrase the president himself, he could stand in the middle of Fifth Avenue and shoot somebody and he wouldn't lose his fundamental support from Republican office holders," he writes.
"Their fate is tied to his, and they will do what they can to shield him from political harm."
DAMNING STATEMENT
Comey's statement reveals the President demanded his loyalty several times and also urged him to let go" of its investigation into his former national security adviser Michael Flynn.
It further reveals how he was pressured to "lift the cloud" of the FBI probe into Russian meddling in the election,
Mr Flynn resigned after misleading White House staff about conversations he had with Russian ambassador to the US Sergey Kislyak.
In an Oval Office meeting on February 14, the President told Comey how Flynn "hadn't done anything wrong in speaking with the Russians, but he had to let him go because he had misled the Vice President".
"He is a good guy and has been through a lot," Trump said, according to Comey.
"I hope you can see your way clear to letting this go, to letting Flynn go. He is a good guy. I hope you can let this go."
CNN commentator Jeffrey Toobin said Trump's actions in this episode amounted to "obstruction of justice".
"There is a criminal investigation going on of one of the President's top associates, his former national security adviser, one of a handful of the most important people in the government. He gets fired, he's under criminal investigation and the President brings in the FBI investigator and says, 'Please stop your investigation,'" he said.
"If that isn't obstruction of justice, I don't know what is."
Comey said he didn't drop the investigation and he didn't think the President was pressuring him to drop the investigation all together.
Comey was spectacularly fired by the US President last month.
"He thinks, 'I tweeted my way to the presidency,' and he's determined to tweet," he said.
