"If I were president of the United States and I had a lawyer that said I could pardon myself, I think I would hire a new lawyer", Senator Grassley told Manu Raju, CNN's senior Congressional correspondent, on the steps of the Capitol on Monday.
Giuliani said that impeachment would be the remedy for a president's illegal behavior, offering as an example the hypothetical case of Trump shooting Comey rather than firing him, the HuffPost reported.
Later in the same program, former New Jersey governor Chris Christie, a Republican, also dismissed the argument put forward by the Trump legal team that the president inherently can not obstruct justice.
White House press secretary Sarah Sanders repeatedly refused Monday to account for the discrepancy between contradictory statements she and President Donald Trump's lawyers made about the President's role in dictating the 2016 Trump Tower meeting response.
Many legal experts say the President's actions could be considered obstruction if prosecutors can show he acted with "corrupt intent".
"Thankfully, the president hasn't done anything wrong and wouldn't have any need for a pardon", Sanders said when first asked about Trump's tweeted claim.More news: Howard Schultz is stepping down as Starbucks’ executive chair
Nevertheless, Trump's lawyers are "trying to come up with a narrow group of conditions in which" Trump could testify before Mueller's team, "if we can justify the fact that they have an open mind and that they'll conclude the investigation".
This followed a report in the Washington Post that Trump had been making enquiries about his power to pardon his family, aides and himself.
US President Donald Trump signs a document reinstating sanctions against Iran after announcing the US withdrawal from the Iran Nuclear deal.
"If he terminated an investigation of himself it could lead to all kinds of things". "It is hard to imagine judicial backing of these views", said Mark Rozell, dean of the Schar School of Policy and Government at George Mason University and author of a book on presidential powers.