An 18-month joint study with the US and the UK is due to be completed by early next year, but staffers from a high-powered US Senate committee have been visiting Australia for talks this week.

Newly tabled responses to Senate questions on notice show the nuclear-powered submarine taskforce has an approved budget of $120m for the 2021-22 financial year and $180m for 2022-23.

That would include funding for technical studies and travel. It would also cover contributions to other government entities which are supporting the taskforce, such as the Department of Foreign Affairs and Trade and nuclear agencies Ansto and Arpansa.

costs of actually building the submarines are yet to be allocated in the budget