WILMINGTON, Del./MOSCOW, Dec 30 (Reuters) - U.S. President Joe Biden and his Russian counterpart Vladimir Putin on Thursday warned each other that an escalation of tensions over Ukraine could rupture relations between the two countries, U.S. and Russian officials said. But the two leaders appeared set to move forward with further diplomatic engagement following their second call this month. "He made clear that the United States and its allies and partners will respond decisively if Russia further invades Ukraine," White House press secretary Jen Psaki said in a statement. Putin told Biden that any sanctions could rupture ties between Russia and the United States and would be a big mistake, the Kremlin said. But Kremlin aide Yuri Ushakov said Russia was satisfied with their phone conversation, which he said centered on security guarantees that Moscow wants from the West amid a build-up of Russian forces close to the Ukrainian border. The call, which was requested by Putin, began at 3:35 p.m. Eastern time (2035 GMT) and ended 50 minutes later, according to U.S. officials.