Hillary Clinton said on Wednesday she suspects President Donald Trump's campaign gave guidance to Russian government propaganda efforts during last year's US presidential campaign, leveling her most serious charge yet against the person who defeated her.The former Democratic presidential candidate, appearing at a tech conference near Los Angeles, said propaganda spread on sites such as Facebook helped cost her the election, and she urged Silicon Valley firms to move faster to stop false stories.Trump has said that there was no collusion between his campaign and Russia.Echoing assessments of US intelligence agencies, Clinton said the Russian government wanted to spread disinformation about her. But she added they "could not have known how best to weaponize that information unless they had been guided.""Guided by Americans?" asked Walt Mossberg, a technology journalist interviewing Clinton on stage."Guided by Americans and guided by people who have polling and data," Clinton responded.She was pressed by another journalist on stage, Kara Swisher, who asked: "But you're leaning Trump?""Yes, I think it's pretty hard not to," Clinton said. She said there had been a "marriage" of people who spread false stories with Republicans who had detailed voter data.It appeared to be the first time Clinton had accused Trump of collusion with Russians. Earlier this month, she blamed Russian hackers and then-FBI Director James Comey for costing her the election.The White House on Wednesday referred questions about Russia to Trump's outside counsel, Marc Kasowitz. He could not immediately be reached.