Facebook CEO Mark Zuckerberg held an unannounced meeting with President Trump during his visit to Washington on Thursday, Axios has learned.Why it matters: With Facebook under pressure from regulators and lawmakers on privacy and other issues, Zuckerberg turned to personal diplomacy with the president on his first visit to D.C. since he testified before Congress last April. Zuckerberg also ate dinner with a group of senators on Wednesday and held a number of meetings on Capitol Hill.A Facebook spokeman told Axios: “Mark is in Washington, D.C., meeting with policymakers to hear their concerns and talk about future internet regulation. He also had a good, constructive meeting with President Trump at the White House today."Go deeper: Top regulators battle to crack down on Big Tech giants