A bipartisan group of Senators unveiled a bill to regulate political ads online that's aimed at stemming a repeat of Russia's meddling in the 2016 election.

The bill, sponsored by Democratic Senators Mark Warner of Virginia and Amy Klobuchar of Minnesota as well as Republican Senator John McCain of Arizona, would extend political advertising disclosure laws that already govern radio and television to ads placed on platforms such as Facebook (FB) - Get Report , Twitter (TWTR) - Get Report and Alphabet's (GOOGL) - Get Report Google.

"We understand that election security is national security," Klobuchar, who is ranking member of the Senate Rules Committee, said at a press conference Thursday announcing the bill.

The Honest Ads Act seeks to help prevent foreign actors from influencing elections by ensuring that political ads sold online are covered by the same rules and regulations that cover other mediums. Digital advertising reached $1.4 billion in the 2016 election, a more than 750% increase from 2012. Warner said that 85% of political ad spending goes to Google and Facebook.

According to Recode, which secured a copy of the bill before its full text was released, the legislation would require any website, web app, search engine, social network or ad network that has 50 million or more unique visitors or annual users to make new data about their ads available for public viewing, including copies of ads, information about who bought them, who they were targeted to and how much they cost.

Companies would also have to employ "reasonable efforts" to ensure foreign governments and agents are not purchasing ads on their platforms. The threshold for mandatory disclosure will be $500.

"The companies we're talking about here are really iconic American companies," Warner, who is vice chairman of the Select Committee on Intelligence, said at Thursday's presser. "I think this is a light touch approach."

McCain said in a statement that it is "more important than ever" to strengthen America's defenses and lamented that transparency in campaigns haven't kept pace with technology.

Tech companies have come under heavy scrutiny in the wake of revelations Russian agents used them to manipulate the 2016 election. Executives from Facebook, Google and Twitter will travel to Capitol Hill on November 1 to testify before Congress.

Warner on Thursday said revelations that $150,000 in Facebook ads bought in Russian rubles are the "tip of the iceberg" of what may have happened. He cited a BuzzFeed News report on Wednesday that it took Twitter 11 months to close a Russian troll account that claimed by speak for the Tennessee Republican Party.

Figures on both sides of the aisle have sounded the alarm bells.

Former President George W. Bush speaking at an event in New York on Thursday warned that America is "experiencing the sustained attempt by a hostile power to feed and exploit our country's divisions." And called for securing "our electoral infrastructure and protect our electoral system from subversion."

"The 2016 elections exposed glaring holes in our ability to police foreign intervention in US elections, and these bills are an appropriate, bipartisan disclosure remedy," said Trevor Potter, president of Campaign Legal Center and a former Republican Chairman of the Federal Election Commission, in a statement. "Voters have a right to be fully informed about who is trying to influence their vote, particularly foreign powers whose motives are contrary to American interests."

The legislation's future in Congress is unclear, though Warner said he believed a number of Republicans would support it as well as Democrats.

"We stand with lawmakers in their effort to achieve transparency in political advertising," said Erin Egan, vice president of U.S. public policy at Facebook, in an emailed statement to TheStreet. "We have already announced the steps Facebook will take on our own and we look forward to continuing the conversation with lawmakers as we work toward a legislative solution."

"We support efforts to improve transparency, enhance disclosures, and reduce foreign abuse," said a Google spokesman in an emailed statement. "We're evaluating steps we can take on our own platforms and will work closely with lawmakers, the FEC and the industry to explore the best solutions."

A Twitter spokesman did not immediately return requests for comment.

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Updated with comment from Google.