The ongoing conflicts between Ukraine and Russia and the geopolitical threats in the Middle East are a serious threat to the world's economy, according to WPP's boss Sir Martin Sorrell.WPP, the world's largest advertising group, saw its pre-tax profit rise to £532m in the first six months of 2014, a 1.5% increase year-on-year and said its net sales operating margin improvement target for the full year remained 0.3%.Sorrell, however, warned that despite a positive first half in its Russian division the group's profits could suffer from the sanctions the US and the EU have imposed on Russia."The strength of sterling has ravaged [...] our revenue figures and profits figures on a reported basis," Sorrell is quoted as saying in the Independent.WPP announced its reported revenues rose £2.7% to £5.47bn, while its net sales margin for the six months ended June 30 was 13%.WPP shares were up 1.63% to 1,247p at 16:14 on Tuesday.