Washington - US President Donald Trump on Friday said a deadly attack in Paris claimed by the Islamic State group "will have a big effect" on France's upcoming presidential vote."Another terrorist attack in Paris. The people of France will not take much more of this. Will have a big effect on presidential election!"Trump tweeted hours after a gunman shot dead a policeman and wounded two others on the world-famous Champs Elysees boulevard.The attack rocked France's presidential race on Friday with just days to go before one of the closest races in recent memory.Bloodshed had long been feared ahead of Sunday's first round of voting after a string of jihadist atrocities since 2015, and shooting on the world-renowned boulevard forced security to the top of the agenda in the campaign.Three of the four frontrunners called off campaign events planned for Friday in the wake of the attack.France is in a state of emergency and at its highest possible level of alert since a string of terror attacks that began in 2015, which have killed over 230 people.