WASHINGTON - US Attorney General Jeff Sessions on Tuesday denounced as "an appalling and detestable lie" the idea he colluded with Russian meddling in the 2016 presidential campaign but refused to answer a series of questions during a high-stakes Senate hearing.Sessions, a senior member of Republican President Donald Trump's Cabinet and an adviser to his presidential campaign, faced criticism from Democratic senators for declining to answer their questions relating to conversations he had with Trump.Democratic Senator Martin Heinrich accused Sessions of violating his vow to tell the full truth. He told Sessions: “You’re impeding this investigation”Sessions dodged questions about were whether he had discussed FBI director James Comey's handling of the FBI's Russia probe with Trump before the president fired Comey on May 9. Similarly, he did not answer whether Trump had expressed concern to Sessions about the attorney general's March decision to recuse himself from the Russia investigation.Democratic Senator Ron Wyden told Sessions, "I believe the American people have had it with stonewalling. Americans don't want to hear that answers to relevant questions are privileged.""I am not stonewalling," Sessions replied. "I am following the historic policies of the Department of Justice." Sessions said he would not discuss confidential communications with the president.Senator Angus King, an independent, questioned Sessions' legal basis for refusing to answer. Sessions said Trump had not invoked executive privilege regarding the conversations.Executive privilege is a power that can be claimed by a president or senior executive branch officials to withhold information from Congress or the courts to protect the executive branch decision-making process.US intelligence agencies concluded in a report released in January that Russian President Vladimir Putin ordered an effort to interfere in the election to help Trump in part by hacking and releasing damaging emails about Democratic candidate Hillary Clinton.The testimony by Sessions marked the latest chapter in a saga that has dogged the Republican Trump's first five months as president and distracted from his domestic policy agenda including major healthcare and tax cut initiatives."I have never met with or had any conversation with any Russians or any foreign officials concerning any type of interference with any campaign or election in the United States. Further, I have no knowledge of any such conversations by anyone connected with the Trump campaign," Sessions said."The suggestion that I participated in any collusion or that I was aware of any collusion with the Russian government to hurt this country, which I have served with honor for over 35 years, or to undermine the integrity of our democratic process, is an appalling and detestable lie," he said.Sessions is the most senior member of Trump's administration caught up in the controversy over whether associates of the president colluded with Russia to help Trump win the election.SPECIAL COUNSELEven before Sessions testified, attention in Washington swiveled to whether Trump might seek to fire Robert Mueller, named last month by the Justice Department to head a federal probe into the Russia issue.Sessions told the senators that he has confidence in Mueller but said he had "no idea" if Trump did because he had not spoken to the president about the matter. Asked whether he would ever take any action to remove Mueller, Sessions said, "I would not think that would be appropriate for me to do."Such a move would be complicated and potentially politically explosive. Deputy Attorney General Rod Rosenstein, the person who would be responsible for carrying out any such dismissal, told a different congressional panel on Tuesday he would not fire Mueller without good cause and he had seen no such cause.Sessions, a former Republican US senator and an early supporter of Trump's presidential campaign, appeared before the committee just five days after Comey told the panel Trump ousted him to undermine the agency's investigation of the Russia matter. Sessions had written a letter to Trump recommending Comey's firing.In March he acknowledged he met twice last year with Russia's ambassador to Washington, Sergei Kislyak. Sessions said he did not mislead Congress because the encounters were part of his job as a US senator, not as a Trump campaign representative. But Sessions recused himself from the Russia investigation in March after the revelations of the two Kislyak meetings.The abrupt dismissal of Comey prompted Trump's critics to charge that the president was trying to interfere with a criminal investigation.Asked about media reports that he had met with Kislyak on a third occasion at a Washington hotel last year, Sessions testified that did not remember meeting or having a conversation with the ambassador at the event. Sessions said he "racked my brain" and had no meeting with any Russian in his capacity as a Trump campaign adviser.Sessions said he did not recuse himself because he felt he was a subject of the investigation himself but rather because he felt he was required to by Justice Department rules.