WASHINGTON (AP) — Former special counsel Robert Mueller's warning that Russian interference is still happening "as we sit" is putting pressure on Republican leaders in Congress to join Democrats in passing additional election security legislation.

Senate Majority Leader Mitch McConnell, a Kentucky Republican, halted a bipartisan effort to beef up state election systems ahead of the 2018 election and on Thursday blocked Democrats from pushing forward a House-passed bill to authorize funding for the states.

McConnell said President Donald Trump's administration has already made great strides to enhance election security, and he called the House bill "not a serious effort" coming from the same side that he said spent the past two years "hyping" Mueller's investigation into Russian interference in the 2016 election.

"Obviously, it's very important that we maintain the integrity and security of our elections," McConnell said Thursday.

The Senate already unanimously approved one bipartisan measure, which makes interference in elections a violation of immigration law. But Democrats — and some Republicans — say Congress must do more.

A report issued by the Senate Intelligence Committee says the Russian government directed "extensive activity" against U.S. election systems ahead of the 2016 presidential election.

The report, released Thursday, says states weren't appropriately warned of the threat against their systems and warns many of them still have outdated voting machines.

The nation's intelligence chiefs say Russia remains intent on disrupting U.S. elections after attempting to breach the election systems of 21 states in 2016. There is no evidence that any votes were changed.

The Senate Democratic leader, Chuck Schumer of New York, called inaction a "disgrace" and is pledging to keep putting forward requests for votes on bills.

Mueller's testimony "should be a wake-up call," Schumer said.

"Leader McConnell, let me read you that sentence," Schumer said from the Senate floor, citing Mueller's testimony Wednesday about Russian interference. "'It wasn't a single attempt. They're doing it as we sit here, and they expect to do it in the next campaign.'"

On Thursday, Schumer tried to push forward consideration of the House-passed bill that would authorize $775 million in grants over the next two years to help states secure their voting systems. It also would prohibit voting systems from being connected to the internet or wireless technologies and tighten standards for private companies that provide election infrastructure.

Republicans said Thursday that money has already been allocated from an earlier spending bill and that no new funding is needed immediately.

Giving a nod to longtime concerns from some states, including those in the South, about maintaining control over election systems, McConnell said any efforts must be done with "extreme care and on a thoroughly bipartisan basis."

Mueller's 448-page report said the Russian government interfered in the 2016 election in "sweeping and systematic fashion." The Russian influence campaign produced fake Facebook and other social media postings that were viewed by millions of Americans. Hackers gained access to some voter databases in Florida.

As action in Congress has stalled, federal agencies have moved to address the problem on their ends.

The director of national intelligence, Dan Coats, established a new elections threats executive position last week. Meanwhile, the National Security Agency director and Cyber Command chief, Gen. Paul Nakasone, created a new cybersecurity directorate focused on election security.

But time may be running out to address concerns in the states before the next election.

The most pressing issue is replacing electronic voting machines that do not produce a paper record of each ballot cast that is verified by the voter and can later be audited.

In 2018, 10 states had more than half of their jurisdictions using such machines, which cybersecurity experts have warned are vulnerable to hacking and must be replaced.

Even if Congress were immediately to send funds to states to replace voting equipment, it would be extremely difficult to make substantial upgrades in time for the 2020 elections. It can take months to decide on replacement machines, develop security protocols, train workers and test the equipment.

Some states have opted to move ahead with replacing these machines by the 2020 elections, but others have not.

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Associated Press writers Tami Abdollah in Washington and Christina Almeida Cassidy in Atlanta contributed to this report.