A US Senate subcommittee investigating former health official Dr Anthony Fauci has obtained a copy of his government iPhone ahead of a planned vote on whether to hold him in contempt of Congress.

According to CNN, the Department of Health and Human Services provided the device to the Senate Homeland Security Permanent Subcommittee on Investigations, chaired by Republican Senator Ron Johnson.

Johnson said the phone could help investigators after Fauci declined to answer questions during a congressional hearing last week, repeatedly invoking his Fifth Amendment right against self-incrimination.

"Hopefully, this device will address many of the questions he refused to answer at last week’s hearing," Johnson wrote on social media.

Republican Senator Rand Paul, who chairs the full Senate Homeland Security and Governmental Affairs Committee, previously subpoenaed Fauci to testify as part of an investigation into the Covid-19 pandemic.

The committee is due to vote on Thursday on a resolution to hold Fauci in contempt of Congress. Paul said that, if approved, the matter would be referred to the US Department of Justice.

According to CNN, Republicans argue Fauci's refusal to answer questions has hindered their investigation, while Democrats have described the inquiry as part of a long-running political effort targeting the former director of the National Institute of Allergy and Infectious Diseases.