Joe Biden heads to the Middle East on potentially the riskiest trip of his presidency Tuesday, aiming to thread the needle between supporting Israel against Hamas, averting catastrophe in Gaza and preventing a regional war. Biden made a top-secret trip to war-torn Ukraine last year to demonstrate US support for the pro-Western country's battle against Russian invasion. - 'Right time' -Asked if Washington expected Israel to wait until after Biden's trip to launch any ground offensive, National Security Council spokesman John Kirby said, "we're not dictating terms or operational directions to the Israelis." The world, and America's rivals like China and Russia, will be watching the results of Biden's trip closely. The most powerful nation in the history of the world," Biden said in an interview broadcast on the CBS News program 60 Minutes at the weekend.