Hong Kong (CNN) Steve Bannon left the White House because the Trump administration "needed a wingman outside" and now wants to help get allies of President Donald Trump elected to the Senate, he said Tuesday at a global investment conference.

Bannon delivered a keynote address in Hong Kong on the subject of "American economic nationalism, the populist revolt and Asia" at an event organized by Hong Kong brokerage firm CLSA. He also discussed the US relationship with China and his belief that a trade war between the two nations can be avoided.

"I left the White house because Trump needed a wingman outside, helping candidates for the Senate," Bannon said, according to a global investor who attended the talk. Media was barred from attending the event; asked why media access was revoked, a CLSA spokesperson said it was a decision by the firm and declined to comment further.

Asked if Bannon received a fee for his speech, the spokesperson had no comment.

In his address, Bannon emphasized the populist movement he pushed while serving as White House chief strategist.

"This populist message is a global message," he said in the Grand Ballroom in the Grand Hyatt Hong Kong. "This movement could win elections for the next 50 years."

A source close to Bannon told CNN on Sunday that he and his allies are preparing primary challenges against Republican senators, including Tennessee Sen. Bob Corker, Mississippi Sen. Roger Wicker, Alabama Sen. Luther Strange, Nevada Sen. Dean Heller and Arizona Sen. Jeff Flake. Bannon has held private meetings with possible challengers whom he plans to support in the primaries, Politico has reported

He has begun working with conservative mega-donor Robert Mercer and has installed an ally in an outside group that is expected to target GOP lawmakers and push Trump's agenda, the article said.

Bannon, who rarely speaks publicly or gives interviews, played a crucial role as one of Trump's top political advisers over the past year, feeding and encouraging Trump's nationalist and populist instincts. While serving in the White House, he garnered an infamous reputation as a puppet master pulling the strings in the Oval Office, earning the moniker "The Great Manipulator" from Time magazine.

During the forum, Bannon reiterated his belief that the Republican establishment is trying to "nullify" Trump's election, a remark he also made while appearing on CBS's "60 Minutes." "The Republican establishment is really trying to nullify Trump's election," he repeated. During the CBS interview, Bannon specifically named Senate Majority Leader Mitch McConnell and House Speaker Paul Ryan as obstacles to Trump's agenda.

He also addressed Trump's recent deal with Senate Minority Leader Chuck Schumer and House Minority Leader Nancy Pelosi to attach hurricane relief money to a shorter-term bump in the debt ceiling as well as keeping the government open.

Trump surprised the leaders of his own party in Congress when he made the deal, making it one of the most fascinating and mysterious moves he's made with Congress during eight months in office.

"He's a transaction guy," Bannon said, defending Trump's decision to work with the Democrats. But he later added: "My recommendation would be not to work with the Democrats."

Says trade war with China can be avoided

Although Bannon has been critical of China in the past, he was very complimentary about China's leadership -- a stark contrast to what he told The New York Times last week, when he compared China to Germany before the rise of the Nazis.

"Trump doesn't respect anyone more than the President of China," Bannon said. "There is a lot of affinity between China and the US."

He added that he believes a trade war with China can be avoided, but called for a bilateral trade agreement with Japan and said the US "must limit China's access to the tech market."

Bannon's praise of China is particularly notable as he is one of the foremost opponents of China in Trump's orbit in regard to economic policy. Right before he left the White House in August, Bannon declared in an interview with The American Prospect that the US is at "economic war with China," promising aggressive trade actions against Beijing and adding he was "fighting" other top White House aides on the subject "every day."

Bannon was ousted in mid-August amid a reshuffling of power within the White House, just a few weeks after retired Marine Corps Gen. John Kelly took over as chief of staff with a goal of instilling order in a chaotic operation beset by internal divisions, staff infighting and a string of controversies.

Bannon has since returned to his role as executive chairman at the conservative online publication Breitbart News, a job he held before joining Trump's campaign.