ARE DESPERATELY TRYING TO CHANGE THEIR MINDS. GABE GUTIERREZ EXPLAINS. >> Reporter: THIS IS U.S. STEEL, RESPONSIBLE FOR SOME 4,000 JOBS ACROSS PENNSYLVANIA. AND NOW AT THE CENTER OF A FIGHT THAT'S GROWING MORE HEATED. WHAT FRUSTRATES YOU THE MOST ABOUT ALL THIS? >> I THINK THAT IT'S A LACK OF CONCERN, YOU KNOW. YOU'RE RIGHT, I'M PISSED. >> Reporter: CHRIS KELLY, A DEMOCRAT IS THE MAYOR OF WEST MIFFLIN, A SMALL TOWN NEAR WEST PITTSBURGH WITH THE STEEL PLANT. HIS GARAGE IS ALSO HIS OFFICE. AT FIRST HE WAS SKEPTICAL WHEN A JAPANESE COMPANY, NIPPON SAID IT WANTED TO BUY U.S. STEEL. BUT HE SAYS NIPPON WON HIM OVER BY PROMISING BILLIONS OF DOLLARS IN LOCAL INVESTMENTS. >> I LEARNED WHAT THE DEAL IS ABOUT, WHAT THE OFFER IS, THE PROTECTION OF JOBS, TO PROTECT PENSIONS, PROTECTION AND MODERNIZATION. >> Reporter: NOW TWO PEOPLE FAMILIAR WITH THE MATTER TELL NBC NEWS THAT PRESIDENT BIDEN IS PREPARING TO ANNOUNCE THAT HE WILL FORMALLY BLOCK THE SALE. EARLIER THIS WEEK, VICE PRESIDENT HARRIS SAID SHE OPPOSED IT TOO. >> U.S. STEEL SHOULD REMAIN AMERICAN-OWNED AND AMERICAN-OPERATED. >> Reporter: FORMER PRESIDENT TRUMP IS ALSO AGAINST THE SALE, BUT U.S. STEEL CEO IS WARNING WITHOUT NIPPON'S MONEY, SHEILA TO PULL OUT OF WESTERN PENNSYLVANIA, COSTING THOUSANDS OF JOBS, INCLUDING PERHAPS TROI STEVENSON'S. HE HAS WORKED AT U.S. STEEL FOR 27 YEARS. HOW WORRIED ARE YOU ABOUT YOUR JOB IF THIS DEAL FALLS THROUGH? >> VERY, VERY. I MEAN WE WORRY ABOUT OUR JOBS ALL THE TIME. RIGHT NOW WITH WHAT WE KNOW, WE FEEL LIKE NIPPON IS THE BETTER DEAL. >> Reporter: STILL, UNION LEADERSHIP ARGUES THAT DEAL WOULD BENEFIT STOCK HOLDERS, NOT WORKERS, AND IT DOESN'T BELIEVE THE CEO'S THREAT. >> I THINK IT IS THE MOST BASELESS, IRRESPONSIBLE THREAT AND STATEMENT THAT ANY CEO COULD POSSIBLY MAKE. >> Reporter: MAYOR CHRIS KELLY, THOUGH, THINKS HIS TOWN IS CAUGHT IN THE MIDDLE. >> I BELIEVE EVERYBODY IS BEING PLAYED AS A PAWN. >> Reporter: AND AS THE PRESIDENTIAL CAMPAIGN INTENSIFIES IN WESTERN