Sources in the US Department of Defense have reported that the first US Abrams tanks have already been delivered to Ukraine – several months earlier than initial estimates.

Ukrainian President Volodymyr Zelenskyy later confirmed that the tanks were already in Ukraine: "Abrams [tanks] are already in Ukraine and are coming to reinforce our brigades. I am grateful to our allies for fulfilling the agreements! We are looking for new contracts and expanding the geography of supply."

More M1 Abrams tanks will be sent in the coming months, the US officials said, noting that the tanks sent to Ukraine on Saturday were the first of 31 the Biden administration has promised to send, as The New York Times rerports.

The officials did not specify exactly how many tanks had been delivered so far.

Politico had previously reported that 10 tanks would be sent to Ukraine initially.

The M1 Abrams will join other tanks in Ukraine's arsenal that it can use to advance and possibly liberate Russian-held territory in Ukraine's eastern and southern regions.

Last week, US President Joe Biden and US Defense Secretary Lloyd Austin predicted that the tanks would be sent within days. Their arrival is part of an effort by Western allies to deliver powerful weapons months ahead of schedule.

The Biden administration announced its intention to send Abrams tanks to Ukraine in January. It took this step after months of insisting that the tanks were too complex and difficult to maintain and repair to induce Germany to supply Leopard tanks.

The first batch of Abrams tanks which the US is providing to Ukraine was approved for shipment in early August.

One of the latest US aid packages includes depleted-uranium shells for the Abrams.