Interfaith Medical Center serves a largely Caribbean-American and poor population in Bedford-Stuyvesant and north-central Brooklyn. Interfaith's chief executive, Luis Hernandez, said this week that while the hospital was making payroll and paying vendors, it had only 18 days to 20 days of cash on hand and it had not been able to pay interest on its state-backed mortgage since November. The chairman of Interfaith's board of trustees, Nathan M. Barotz, blamed Wyckoff Heights Medical Center, in Bushwick, for Interfaith's plight; he accused Wyckoff's administration of dragging its heels on a plan to shore up operations by combining the operations of Interfaith, Wyckoff and Brooklyn Hospital Center, in Fort Greene.