Under pressure from President Donald Trump, the US Justice Department has asked its inspector general to assess whether political motivation tainted the FBI investigation into ties between Russia and Trump's campaign. Officials hoped the step might avert a larger clash between the President and federal law enforcement officials, The Washington Post reported on Sunday. Trump, who spent much of Sunday rallying against the year-old special counsel probe, tweeted that "I hereby demand, and will do so officially tomorrow, that the Department of Justice look into whether or not the FBI\/DOJ infiltrated or surveilled the Trump Campaign for Political Purposes - and if any such demands or requests were made by people within the Obama Administration!" Hours later, the Justice Department responded by saying it had asked its inspector general to expand an ongoing review of the applications to monitor a former Trump campaign adviser "to include determining whether there was any impropriety or political motivation in how the FBI conducted its counterintelligence investigation of persons suspected of involvement with the Russian agents who interfered in the 2016 presidential election." The department noted that a US attorney would be consulted if evidence of criminal conduct was found. "If anyone did infiltrate or surveil participants in a presidential campaign for inappropriate purposes, we need to know about it and take appropriate action," Deputy Attorney General Rod J. Rosenstein said in a statement. Sunday's developments came in the wake of reports that a long time US intelligence source assisted the investigation into Russian election interference now overseen by special counsel Robert S. Mueller III. Trump and his allies have seized on the informant's role to claim that the FBI spied on his campaign. There is no evidence to indicate an intelligence source was embedded within the campaign, as the president has suggested.