BEIJING (Reuters) -China's top diplomat, Wang Yi, begins on Monday a four-day trip to Russia during which both nations are expected to pledge deeper mutual political trust, readying for a possible landmark visit by President Vladimir Putin to Beijing in October. Wang, who heads the foreign ministry as well as the ruling Communist Party's foreign affairs office, will meet Security Council Secretary Nikolai Patrushev for annual security talks, the Chinese foreign ministry said in a statement. The veteran diplomat's talks with counterpart Sergei Lavrov will cover a "wide range of issues" including "contacts at higher and the highest levels," the Russian foreign ministry said last week.