Lawyers for US President Donald Trump on Tuesday said they have submitted his written response to questions posed by Special Counsel Robert Mueller, who is investigating allegations of Russian interference in the 2016 presidential election and the Trump campaign's collusion with them. "The president today answered written questions submitted by the Special Counsel's Office. The questions presented dealt with issues regarding Russia-related topics of the inquiry. The president responded in writing," Jay Sekulow, the president's counsel, said in a statement. Trump's personal lawyer Rudy Giuliani also issued a statement. "It has been our position from the outset that much of what has been asked raised serious constitutional issues and was beyond the scope of a legitimate inquiry. This remains our position today," he said in his statement. "The president has nonetheless provided unprecedented cooperation. The Special Counsel has been provided with more than 30 witnesses, 1.4 million pages of material, and now the president's written responses to questions. It is time to bring this inquiry to a conclusion," Giuliani said. Trump's submission comes nearly a year after Mueller, a former FBI director, first indicated to his legal team that he was interested in questioning the president, the Wall Street Journal said. Trump had said these were easy questions, and he had no difficulties in responding to them. He has repeatedly asserted that neither he nor his campaign had any collusion with the Russians. According to the New York Times, Mueller has declined to rule out trying to compel Trump to sit for an interview after reviewing his written answers. "I'm sure they're tricked up," Trump told reporters on Friday, "because, you know, they like to catch people". "So you have to always be careful when you answer questions with people that probably have bad intentions," he said.