House Speaker Nancy Pelosi plans to announce a formal impeachment inquiry of President Donald Trump over allegations that he pressured the leader of Ukraine to investigate Joe Biden’s family, it is claimed.

Ms Pelosi’s likely decision was described to The Associated Press by a person familiar with the decision.

Ms Pelosi is set to make an announcement at 5pm local time.

Ms Pelosi had for months resisted calls to start the impeachment process.

But the dynamic changed this week as more members of her caucus came out in support, including Democrats from swing districts.

Democrats are demanding information about whether President Trump improperly pressured the Ukrainian president to investigate Mr Biden and his son, partly by withholding foreign aid.

President Trump insists he did nothing wrong and said he will release an unredacted transcript of a call with Ukraine’s leader on Wednesday.