Asked by a reporter if he would take action against President Vladimir Putin, whom he will meet for a summit in Geneva later this month, Biden said: "We're looking closely at that issue."

The ransomware attack on a US subsidiary of Brazilian-owned JBS has again prompted accusations that Russia is at least harboring cybercriminals.

Similar suspicions were raised after ransomware hackers forced the temporary shutdown of the huge Colonial fuel pipeline in the eastern United States last month.

Asked if Putin is testing him ahead of their summit, Biden said "no."

The Federal Bureau of Investigation on Wednesday attributed the attack to "REvil and Sodinokibi," which experts have said are two names for the same hacking group with ties to Russia, and said it was "working diligently to bring the threat actors to justice."

"We continue to focus our efforts on imposing risk and consequences and holding the responsible cyber actors accountable," the FBI said in a statement.

The White House says Biden will bring up US concerns during the summit on June 16, as well as at earlier summits with allies in the G7 group, the European Union and NATO.

"We expect this to be an issue of discussion throughout the president's trip," Press Secretary Jen Psaki told reporters.

"Harboring criminal entities that are intending to do harm, that are doing harm to the critical infrastructure in the United States, is not acceptable," she said.

"We're not going to stand by that. We will raise that and we're not going to take options off the table."

The White House has not blamed the Kremlin directly, only suggesting that criminal groups are operating from inside Russia. However, Psaki said "responsible states do not harbor" cybercriminals.

"President Biden certainly thinks that President Putin and the Russian government has a role to play in stopping and preventing these attacks. Hence, it will be a topic of discussion when they meet," she said.

For its part, Russia said Wednesday it would be open to any US request for help in investigating the cyberattack.

JBS is a sprawling meat supplier with operations in the United States, Australia, Canada, Europe, Mexico, New Zealand and Britain. 

The company said the vast majority of its beef, pork, poultry and prepared foods plants would be operating "at near full capacity" on Thursday.

JBS "is not aware of any evidence at this time that any customer, supplier or employee data has been compromised," it said in a statement late Wednesday.

"Given the progress our teams have made to address this situation, we anticipate operating at close to full capacity across our global operations tomorrow (Thursday)," said JBS USA CEO Andre Nogueira.