By Patricia Zengerle
WASHINGTON (Reuters) - The U.S. Senate Intelligence Committee chairman said on Wednesday the issue of whether President Donald Trump's 2016 election campaign colluded with Russia remains an open question as the panel intensifies its probe into the matter.
Republican Chairman Richard Burr and Democratic Vice Chairman Mark Warner also warned about the risk to future U.S. elections posed by Russia, including what is expected to be a closely contested election next month for governor of Warner's home state, Virginia.
Burr told reporters the committee plans to conduct 25 more interviews with witnesses this month, with a goal of finishing the main congressional investigation into Russian meddling in the election by the end of 2017.
"The issue of collusion is still open," said Burr, standing alongside Warner. "We have not come to any determination on collusion," Burr added.
Trump, who has called allegations of campaign collusion with Moscow a hoax, has faced questions about the matter since he took office in January. A special counsel appointed by the Justice Department, Robert Mueller, is conducting a separate probe that potentially could lead to criminal charges against figures in the investigation. Russia denies meddling.
U.S. intelligence agencies concluded that Russia interfered in the election to try to help Trump defeat Democratic candidate Hillary Clinton through a campaign of hacking and releasing embarrassing emails and other propaganda efforts. Burr said the committee agreed with the intelligence community's conclusion that Russia had interfered.
"The committee continues to look into all evidence to see if there was any hint of collusion," Burr said. "Now, I'm not even going to discuss initial findings because we haven't any. We've got a tremendous amount of documents still to go through."
100 INTERVIEWS, 250 HOURS
He said the panel has conducted more than 100 interviews lasting more than 250 hours in its nine-month-old investigation, and "we currently have booked for the balance of this month 25 additional interviews."
Those already interviewed include the president's son-in-law and adviser Jared Kushner, former Trump campaign manager Paul Manafort, and social media executives such as officials from Twitter Inc <TWTR.O>.
Burr urged American political campaigns to take the threat of Russian interference seriously.
"You can't walk away from this and believe that Russia's not currently active in trying to create chaos in our election process. And I assume that the same tactics that you saw in Montenegro, in France, in Belgium and in the United States will continue to be tested within our structure of the election process," Burr said.
Burr said the committee has "hit a wall" in its investigation of a former British spy's explosive dossier on purported Russian support for Trump's 2016 campaign.
Former MI6 officer Christopher Steele compiled the dossier, which Trump was told by former FBI director James Comey contained salacious material about the businessman-turned-president. Trump and his associates have called the dossier's contents false.
"We have, on several occasions, made attempts to contact Mr. Steele, to meet with Mr. Steele," Burr said.
"Those offers have gone unaccepted. The committee cannot really decide the credibility of the dossier without understanding things like who paid for it, who are your sources and sub-sources," Burr added.
(Reporting by Patricia Zengerle; Additional reporting by Makini Brice; Writing by Will Dunham; Editing by Howard Goller)