A woman will soon feature on US bank notes for the first time in 150 years after a successful campaign to celebrate the centenary of female suffrage. But the surprise decision comes with a catch: whoever is chosen will have to share the honour with a man.

Treasury secretary Jack Lew announced the process of redesigning the $10 bill late on Wednesday – less than a week after a high-profile petition was handed to Barack Obama calling on him to pick African-American slavery abolitionist Harriet Tubman.

The public campaign, which nominated the civil war heroine from a shortlist of 15 women, had suggested she replace president Andrew Jackson on the $20 bill.

But officials have opted to redesign the $10 bill instead, currently occupied by the first treasury secretary Alexander Hamilton, and plan a public consultation exercise of their own before making a final decision on who should be the new woman on the note later this year.

Lew also revealed that when the first new bills are printed in 2020 – coinciding with the 100th anniversary of American women receiving the right to vote – they are likely to continue to feature Hamilton: either by also incorporating him in the new design, or by producing several versions.

Harriet Tubman won an online poll last month to replace Andrew Jackson on the $20 bill. Photograph: Chip Somodevilla/Getty Images

"It was personally very important to me to make sure that as we make this decision we continue to honour Alexander Hamilton who played such a formative role in the creation our country, the establishment of democracy as we know it and the principle of the soundness of our currency," Lew told reporters.

Nonetheless, the administration insists its surprise announcement is a "historic decision" in the normally conservative world of US currency production.