(Rewrites, adds Nelson comment)
WASHINGTON, April 9 (Reuters) - Facebook Inc Chief Executive Mark Zuckerberg met U.S. lawmakers individually on Monday and told Congress in written testimony that the social media network should have done more to prevent itself and its members' data being misused.
His conciliatory tone precedes two days of congressional hearings where Zuckerberg is set to answer questions about Facebook user data being improperly appropriated by a political consultancy and the role the network played in the U.S. 2016 election.
"We didnt take a broad enough view of our responsibility, and that was a big mistake," he said in remarks released by the U.S. House Energy and Commerce Committee on Monday. "It was my mistake, and Im sorry. I started Facebook, I run it, and Im responsible for what happens here."
Zuckerberg, surrounded by tight security and wearing a dark suit and a purple tie rather than his trademark hoodie, traversed Capitol Hill on Monday ahead of his scheduled appearance before two congressional committees on Tuesday and Wednesday.
Zuckerberg did not respond to questions as he entered and left a meeting with Senator Bill Nelson, the top Democrat on the Senate Commerce Committee. He is expected to meet Senator John Thune, the Commerce Committees Republican chairman, later in the day, among others.
The message I wanted to convey to him is that if we dont rein in the use of social media, none of us are going to have any privacy anymore," Nelson told reporters after the meeting.
If Zuckerberg does not provide satisfactory answers this week, Congress is more likely to push new legislation to strictly regulate Facebook.
White House economic adviser Larry Kudlow declined to comment on Monday on whether he thought the administration should impose new regulations on Facebook.
Top of the agenda in the forthcoming hearings will be Facebook's admission that the personal information of up to 87 million users, mostly in the United States, may have been improperly shared with political consultancy Cambridge Analytica.
Lawmakers are also expected to press him on a range of issues, including the 2016 election.
"Its clear now that we didnt do enough to prevent these tools from being used for harm..." his testimony continued. "That goes for fake news, foreign interference in elections, and hate speech, as well as developers and data privacy."
Facebook, which has 2.1 billion monthly active users worldwide, said on Sunday it plans to begin on Monday telling users whose data may have been shared with Cambridge Analytica. The company's data practices are under investigation by the U.S. Federal Trade Commission.
London-based Cambridge Analytica, which counts U.S. President Donald Trumps 2016 campaign among its past clients, has disputed Facebooks estimate of the number of affected users.
Zuckerberg also said that Facebook's major investments in security "will significantly impact our profitability going forward." Facebook shares were up 1.7 percent in afternoon trading.
ONLINE INFORMATION WARFARE
Facebook has about 15,000 people working on security and content review, rising to more than 20,000 by the end of 2018, Zuckerberg's testimony said. "Protecting our community is more important than maximizing our profits," he said.
As with other Silicon Valley companies, Facebook has been resistant to new laws governing its business, but on Friday it backed proposed legislation requiring social media sites to disclose the identities of buyers of online political campaign ads and introduced a new verification process for people buying issue ads, which do not endorse any candidate but have been used to exploit divisive subjects such as gun laws or police shootings.
The steps are designed to deter online information warfare and election meddling that U.S. authorities have accused Russia of pursuing, Zuckerberg said on Friday. Moscow has denied the allegations.
Zuckerberg's testimony said the company was "too slow to spot and respond to Russian interference, and were working hard to get better."
He vowed to make improvements, adding it would take time, but said he was "committed to getting it right."
Republican Senator John Kennedy of Louisiana said he wanted candor from Facebook. "Im hoping that Mr. Zuckerberg wont just pull things out of his orifices, that hell talk frankly about what Facebook can and cannot do," he told CNBC.
A Facebook official confirmed that the company had hired a team from the law firm WilmerHale and outside consultants to help prepare Zuckerberg for his testimony and how lawmakers may question him.
(Reporting by David Shepardson and Dustin Volz Editing by Bill Rigby)