FILE PHOTO: Voters cast their ballots to vote in state and local elections at Robious Elementary School in Midlothian, a suburb of Richmond, Virginia, U.S. November 5, 2019. REUTERS/Ryan M. Kelly/File Photo

(Reuters) - The United States should boost spending and take other “aggressive steps” to protect next year’s presidential election from foreign meddling, a group of former national security officials said on Monday.

Citing what they said were signs U.S. rivals want to undermine the November 2020 poll, National Security Action - a group led by former advisers to President Barack Obama - said states and agencies should invest in paper ballot backups for digital voting machines, ensure audits of election results, improve cybersecurity and boost training for poll workers.

Election security has become a major concern since U.S. intelligence agencies claimed Russia interfered in the 2016 presidential election to tilt the vote in Donald Trump’s favor. Moscow has denied here any interference.

Congress has appropriated some $600 million for election security since 2018 and is working to approve another $250 million, an amount that National Security Action called a “modest start.” Its statement was signed by 70 former security officials from a range of agencies.

The group noted that the state of Pennsylvania alone has spent $125 million upgrading voting machines that will be used during 2020 elections.

The former officials said they had “already learned” of attempts by Iran and Russia to undermine the 2020 U.S. elections, though they offered no specific detail.

The White House had no immediate comment.

Trump has warned of plans by U.S. adversaries to interfere in American elections, and last year signed an executive order here that would slap sanctions on foreign countries or people trying to interfere in the U.S. political process.