WASHINGTON (AP) — The Federal Reserve extended its year-long fight against high inflation by raising its key interest rate a quarter-point despite concerns that higher borrowing rates could worsen the turmoil that has gripped the banking system. “The U.S. banking system is sound and resilient,” the Fed said in a written statement. At the same time, the Fed warned that the financial upheaval stemming from the collapse of two major banks is “likely to result in tighter credit conditions” and “weigh on economic activity, hiring and inflation.” The Fed also signaled that it’s likely nearing the end of its aggressive series of rate hikes.