By Idrees Ali and Tom Balmforth RAMSTEIN AIR BASE, Germany/KYIV (Reuters) -Western allies on Friday dampened Ukraine’s hopes for a rapid shipment of battle tanks to boost its firepower for a spring offensive against Russian forces, with the United States urging Kyiv to hold off from mounting such an operation. The United States’ top general, speaking after a meeting of the allies at Ramstein Air Base in Germany, also said it would be very hard for Ukraine to drive Russia’s invading forces from the country this year. The run-up to the Ramstein meeting had been dominated by the issue of whether …