By Robin Emmott and Humeyra Pamuk MADRID (Reuters) – NATO leaders will urge Turkish President Tayyip Erdogan to lift his veto over Finland and Sweden’s bid to join the military alliance when they meet for a three-day summit on Tuesday, as the West strives to send Russia and China a signal of resolve. Taking place in the shadow of Russia’s war in Ukraine, the Madrid gathering comes at a pivotal moment for the transatlantic bond after failures in Afghanistan and internal discord during the era of former U.S. President Donald Trump, who threatened to pull Washington out of the nuclear alliance. N…