"Certainly, if I was Russia, I would not want that [Ukraine becoming a NATO member]. I would also not want Finland and Sweden to be a part of NATO," Austin told the US Senate Armed Services Committee on Tuesday.
Austin also confirmed that the enlargement of NATO over the past year has created "worse conditions" for Russia, essentially admitting that the military bloc poses a threat to the country.
Earlier, US Secretary of State Antony Blinken said that Ukraine will become a member of NATO. He said later in the day that the NATO summit in Washington in July will unveil the role the military bloc should play in supporting Ukraine in the longer term.
Russian President Vladimir Putin has said that NATO's expansion to include Ukraine would create a direct national security threat to Russia and that Moscow considers the non-aligned status of Ukraine to be extremely important to put an end to the years-long conflict.
Ukraine's stated plans to join the alliance were among the reasons for Russia to launch its special military operation in February 2022.