Former White House chief strategist Steve Bannon is a man of his word, according to allies who said the Breitbart chairman is more determined than ever to wage war on incumbent Republicans in 2018 even without President Trump's endorsement.

Hours after Trump decried inaction by congressional Republicans at a Cabinet meeting Monday, during which he seemed to offer a tepid endorsement of Bannon's plan to prop up insurgent GOP candidates, the president emerged from talks with Senate Majority Leader Mitch McConnell, R-Ky., with concerns about an interparty battle.

"I'm going to see if we can talk him out of that," Trump said of Bannon, signaling that there are some Senate Republicans the Breitbart chairman wishes to challenge that the White House may stand by next fall.

Related: Steve Bannon's revolt against Mitch McConnell gets underway

Bannon has been on the hunt for pro-Trump Republicans who could successfully primary at least six GOP senators facing reelection next year and challenge other primary candidates backed by McConnell.

A source close to Bannon said he was unfazed after seeing Trump's muddied comments, and has continued to seek financial backing from major conservative donors for his "season of war against [the] GOP establishment."

"The other side is overplaying their hand by doing a victory lap right now," the source told the Washington Examiner. "Think about what the president didn't say in his press conference with McConnell. He didn't say, 'I'm against Steve Bannon targeting incumbent Republican senators.'"

A separate source, who has previously worked closely with Bannon, said Trump's frustration with the outcome of last month's Senate GOP primary in Alabama is keeping him from explicitly condemning Bannon's strategy "for now."

At the urging of his son-in-law Jared Kushner and allies of McConnell, the president endorsed and later campaigned for Sen. Luther Strange in his unsuccessful runoff race against former judge Roy Moore, an ultra-conservative candidate who earned the support of Bannon and other high-profile Trump supporters.

Asked how detrimental it would be if Trump again lent support to incumbent GOP senators facing insurgent challengers, the source close to Bannon responded: "How bad was it in Alabama?"

For the last several weeks, Bannon has been jetting between both coasts for meetings with GOP megadonors who have spent years contributing to super PACs aligned with McConnell and other establishment forces, Politico reported last week. So far, the former West Wing staffer has sat down with casino magnate Sheldon Adelson, Home Depot executive Bernie Marcus, and venture capitalist John Childs, among others.

A source involved in Bannon's outside group Great America said he has "millions lined up right now" and plans to launch an aggressive ad game once 2018 draws nearer.

He is also looking to mimic a high-profile rally that took place on the eve of Alabama's primary, and featured conservative VIPs like former White House national security aide Sebastian Gorka, former Alaska Gov. Sarah Palin, and Bannon himself, with a nationwide bus tour.

"Will you oppose McConnell?" has already become a litmust test for potential candidates working with Bannon or seeking his support, in addition to rigorous questioning about trade and immigration, said the source close to Bannon.

Many Republicans are still wondering why the nationalist firebrand wants to challenge GOP senators like John Barrasso of Wyoming or Roger Wicker of Mississippi, both of whom voted with the president more than 95 percent of the time – more than Texas Sen. Ted Cruz (93.9 percent), who Bannon has said he will not target.

"I don't understand why, if his goal is to help Donald Trump, why he isn't strictly looking to unseat Democratic senators," said veteran GOP strategist Ford O'Connell. "This basically sends a message that there is no amount of loyalty to Trump that is sufficient to placate Bannon world."

"Trump's problem isn't insufficient loyalty; it's that he needs more senators outside of the 60-vote threshold," O'Connell continued, noting that "the folks who held up the Obamacare repeal aren't up [for reelection] in 2018."

But Bannon sees things differently and has made it clear that a vote for legislation the president supports is not nearly enough to prove a lawmaker has eagerly embraced Trump's agenda.

"Even safe incumbents like Barrasso and Deb Fischer, they have to understand something," Bannon told Fox News' Sean Hannity earlier this month. "Just voting is not good enough. You have to have a sense of urgency."