Previous Bosnian governments have moved over the past decade to join NATO, which called on the Balkan country this month to present its "action plan" -- one of the final measures before a membership invitation can be issued.

But its new nationalist Serb president Milorad Dodik -- who was elected in October alongside Croat and Bosnian Muslim (Bosniak) co-presidents -- has repeatedly stressed his opposition to joining the alliance.

After meeting with the three presidents in Sarajevo, US Assistant Secretary of State John Sullivan said Washington "enthusiastically supports" Bosnia's efforts to pursue NATO membership.

"We discussed the US position, which is as firm as it's ever been," he told reporters.

A consensus is needed for Bosnia to move forward with its membership bid.

But Dodik, who casts himself as close to Russian President Vladmir Putin, shows little sign of bending.

"We have a consensus in the presidency on the European path and I had the opportunity to say that there is no consensus on NATO," Dodik said after meeting the American diplomat.

Many Serbs find joining NATO unpalatable as the alliance helped stop its 1990s intercommunal wars through a bombing campaign on Serb positions.

More than two decades after the war, which killed some 100,000 people, the Balkan country remains sharply split among its three main communities: Bosniaks, Serbs and Croats.

In 2017 Dodik, a hardline Serb nationalist, was sanctioned by the US for his efforts to undermine the country's integrity.

On Monday Sullivan said those sanctions remain in place but that he met with Dodik out of respect for the institution of the presidency.

Under pressure from the West, Bosnia created a single army in 2006 and enshrined NATO membership as an objective in its National Defence Act.