WASHINGTON (AP) -- The White House and its allies are scrambling for ways to offset potential damage from fired FBI Director James Comey's highly anticipated congressional testimony, an appearance that could expose new details about his discussions with President Donald Trump about the federal investigation into Russia's election meddling.

Asked about the testimony, Trump on Tuesday was tight-lipped: "I wish him luck," he told reporters before a meeting with lawmakers.

Tuesday evening, a person familiar with the situation said Comey had asked Attorney General Jeff Sessions to keep him from being alone with Trump.

The person, who was not authorized to discuss the matter by name and spoke on condition of anonymity, told The Associated Press the request was made because of concerns Comey had about Trump.

It was not immediately clear when the conversation occurred. But The New York Times, which first reported the request to Sessions, said it came after Trump had asked Comey in February to end an investigation into Trump's first national security adviser, Michael Flynn.

Trump's White House and its allies are crafting a strategy aimed at undermining Comey's credibility. Both White House officials and an outside group that backs Trump plan to hammer Comey in the coming days for misstatements he made about Democrat Hillary Clinton's emails during his last appearance on Capitol Hill.

An ad created by the pro-Trump Great America Alliance -- a nonprofit "issues" group that isn't required to disclose its donors --  casts Comey as a "showboat" who was "consumed with election meddling" instead of focusing on combating terrorism. The 30-second spot is slated to run digitally on Wednesday and appear the next day on CNN and Fox News.

The Republican National Committee has been preparing talking points ahead of the hearing, which will be aired live on multiple TV stations. An RNC research email Monday issued a challenge to the lawmakers who will question Comey. There's bipartisan agreement, the email says, that Comey "needs to answer a simple question about his conversations with President Trump: If you were so concerned, why didn't you act on it or notify Congress?"

Comey's testimony before the Senate intelligence committee marks his first public comments since he was abruptly ousted by Trump on May 9. Since then, Trump and Comey allies have traded competing narratives about their interactions. The president asserted that Comey told him three times that he was not personally under investigation, while the former director's associates allege Trump asked Comey if he could back off an investigation into Michael Flynn, who was fired as national security adviser because he misled the White House about his ties to Russia.

Democrats have accused Trump of firing Comey to upend the FBI's Russia probe, which focused in large part on whether campaign aides coordinated with Moscow to hack Democratic groups during the election. Days after Comey's firing, the Justice Department appointed a special counsel, former FBI Director Robert Mueller, to oversee the federal investigation.

Despite the mounting legal questions now shadowing the White House, Trump has needled Comey publicly. In a tweet days after the firing, he appeared to warn Comey that he might have recordings of their private discussions, something the White House has neither confirmed nor denied.

White House officials appear eager to keep the president away from television and Twitter Thursday, though those efforts rarely succeed. White House spokesman Sean Spicer said the president plans to attend an infrastructure summit in the morning, then address the Faith and Freedom Coalition's "Road to Majority" conference at 12:30 p.m.

"The president's got a full day on Thursday," Spicer said.

The White House had hoped to set up a "war room" stocked with Trump allies and top-flight lawyers to combat questions about the FBI and congressional investigations into possible ties between the campaign and Russia. However, that effort has largely stalled, both because of a lack of decision-making in the West Wing and concerns among some potential recruits about joining a White House under the cloud of investigation.

"If there isn't a strategy, a coherent, effective one, this is really going to put us all behind the eight ball. We need to start fighting back. And so far, I don't see a lot of fight," said Barry Bennett, a former Trump campaign aide.

Still, Trump supporters say they are willing to step in to help the White House deflect any accusations from Comey.

"If we feel he crosses a line, we'll fire back," said Ed Rollins, chief strategist of Great America PAC, the political arm of the group airing the Comey ad.

Rollins and others with Great America say they plan to stand up for Trump in cable appearances Thursday.

He said the White House has "improved" its communications with surrogates, starting with the president's recent trip abroad, and frequently holds call-ins to discuss what story lines they'd like to push.

"I assume they'll do the same thing with this," Rollins said of the Comey hearing. However, he added, he had not heard from the White House about the Comey hearing as of midday Tuesday.