Trump remained focused on the issue over the weekend, and on Sunday, in an extraordinary tweet, pledged to "demand" a DOJ investigation into whether the Obama administration was behind this supposed politically-motivated spying.
"If anyone did infiltrate or surveil participants in a presidential campaign for inappropriate purposes, we need to know about it and take appropriate action", Rosenstein said.
Trump did not elaborate on the promised "demand", which he included in one of a series of tweets he sent throughout the day Sunday.
Representative Devin Nunes, the Republican chairman of the House Intelligence Committee, has asked the DOJ to turn over documents disclosing why the FBI launched an investigation into the Trump campaign.
A New York Times report described the professor as "an informant", saying the federal agency was looking into evidence that Carter Page and George Papadopoulos had suspicious contacts with Russian Federation.
Meanwhile, House Democrats stood by the Justice Department following the President's demand for an inquiry into the department's actions regarding the Trump campaign.
On Friday, Trump quoted Fox Business Network anchor David Asman in a tweet.
The Associated Press reports that Giuliani said that Mueller's probe could end by September 1 if Mr. Trump were to sit for an interview in July, which is the legal team's new working plan.
"STOP!" he wrote. "They have found no collusion with Russia, No obstruction". He had come under fire for his decision to go to the White House grounds and look at classified information that suggested the Trump transition team may have been under indirect surveillance. The legal team initially said it hoped to make a decision on an interview by May 17, the one-year mark, but lawyer Rudy Giuliani told CBS News he hopes to have a final decision about whether Mr. Trump will sit for an interview with Special Counsel Robert Mueller before the president heads to Singapore for the highly anticipated North Korea summit in mid-June.
White House spokeswoman Sarah Sanders said Sunday she had nothing to add to the President's tweets.
As GOP lawmakers have pressed their demand to see DOJ documents about the identity of the FBI informant, reportedly an American academic who teaches in Britain, critics of the move have warned against the release of such information to Congress ― where details of federal investigations often leak. Although Trump has suggested the source was embedded in his campaign, USA officials have told CNN that was not the case.
"Apparently the DOJ put a Spy in the Trump Campaign".
It was not clear what kind of response Mr Trump was seeking from the Justice Department, since investigations are usually kept secret.
"So if the President really gives Rod Rosenstein or Chris Wray an order (as opposed to Twitter bluster) demanding a particular investigation not properly predicated under FBI/DOJ guidelines for this overtly political goal, I believe both men will resign rather than comply", Wittes wrote.
Another new theme of Trump's top legal adviser Rudolph Giuliani is that if anyone in the Trump campaign did work with Russian Federation to use dirt against Democratic nominee Hillary Clinton, they would not have been doing anything wrong.
Vermont Senator Bernie Sanders announces re-election bid
Sanders faces challengers across the political spectrum, though none have his political status or multimillion dollar campaign fund .