CNN  —  United Auto Workers President Shawn Fain and other members of the union’s board have expressed concerns about President Joe Biden’s ability to beat Donald Trump in November, a source close to the union says. The union is discussing the way forward on how to beat Trump in November, but the group is not considering rescinding its endorsement of Biden at this time, the source added. Reuters was first to report Fain’s concerns. Concerns from the UAW would be significant at a time when Biden is working to shore up support within the labor community. The president spent about 30 minutes at the AFL-CIO headquarters in Washington, DC, on Wednesday, describing the group of union leaders as his “domestic NATO.” After Biden’s drop-by, the group met privately for some time, including hearing from campaign officials. Fain, a vocal Trump critic, is a member of the AFL-CIO’s executive council, which on Wednesday announced it “unanimously voted to reaffirm its commitment to re-electing President Joe Biden and Vice President Kamala Harris, the leadership of the most pro-union administration in our lifetimes.” The UAW formally endorsed Biden in January after months of White House overtures to the union chief. The endorsement was seen as a major boon for Biden as he looked to court working class voters in swing states like Michigan and Wisconsin. The president is set to visit Michigan on Friday as he pushes forward with his campaign in the face of deep reservations within his party over his ability to win in November. A union spokesperson declined to comment on the Reuters report.