The United States is allowing a small number of American defence contractors to work inside Ukraine to maintain and repair Pentagon-provided weaponry, according to US officials.

The US has been a key military backer of Ukraine, committing more than $60bn in security aid since Russia’s full-scale invasion in February 2022. But it has not permitted US military contractors to work in Ukraine, wary that it could be drawn into a direct conflict with Russia.

US President Joe Biden made the decision in a significant policy shift before he leaves office in January, US media reported on Friday, before the November 5 presidential election, won by Donald Trump.

Biden also plans to rush billions of dollars in security assistance to Ukraine before his term ends. Trump has criticised the scale of US military and financial support for Ukraine and has pledged to end the war with Russia quickly – without saying how.

For the past two years, US and allied forces have been providing real-time maintenance advice using phones and tablets to communicate in encrypted chatrooms with Ukrainian forces.

Officials said the Pentagon is allowing the contractors to go because some equipment – including F-16 fighter jets and Patriot air defence systems – require high-tech expertise to repair. Using the contractors, they said, will ensure the weapons are fixed quickly so Ukrainian forces can continue to use them in combat.

The number of contractors would be small and located far from the front lines. They would not be engaged in direct combat, the officials said. The companies will be responsible for the safety of their employees.

The restrictions have sometimes slowed down repairs and proven increasingly difficult as the US has provided Ukraine with more complicated systems, such as the F-16s and Patriot systems.

A lot of equipment is not being used because it is damaged. In August, an F-16 jet crashed while repelling a Russian attack, killing its pilot.

The policy change would move the Pentagon in line with the US Department of State and US Agency for International Development, which already have US contractors in Ukraine.

The decision comes at a critical time in the conflict, as Russia makes more advances into Ukrainian territory.

It is unclear, however, how sustainable the policy shift will be with so little time left in Biden’s administration. Trump takes office on January 20.

President Volodymyr Zelenskyy has urged his Western allies to allow Ukraine to use long-range missiles to hit targets inside Russia and increase pressure on Moscow to end the war.