The original plan was to send Ukraine 31 of the newer M1A2 Abrams, which could have taken a year or two to build and ship. But officials said the decision was made to send the older M1A1 version, which can be taken from Army stocks and could be there before the end of the year. Officials said the M1A1 also will be easier for Ukrainian forces to learn to use and maintain as they fight Russia’s invasion.

The officials spoke on Tuesday on the condition of anonymity because the plan has not yet been publicly announced. Pentagon officials are expected to make the announcement Tuesday.

The Biden administration announced in January that it would send the tanks to Ukraine — after insisting for months that they were too complicated and too hard to maintain and repair. The decision was part of a broader political maneuver that opened the door for Germany to announce it would send its Leopard 2 tanks to Ukraine and allow Poland and other allies to do the same.

It’s unclear how soon the U.S. would begin training Ukrainian forces on how to use, maintain and repair the tanks. The intention would be to have the training of the troops coincide with the refurbishment of the tanks, so that both would be ready for battle at the same time later this year. The Pentagon will also have to ensure that Ukrainian forces have an adequate supply chain for all the parts needed to keep the tanks running.

Any delivery of the tanks would not likely happen in the spring months, when both Russia and Ukraine are expected to launch more intensive offensives. The two sides have been largely in a stalemate, trading small slices of land over the winter.

The fiercest battles have been in the eastern Donetsk region, where Russia is struggling to encircle the city of Bakhmut in the face of dogged Ukrainian defense. Local Gov. Petro Kyrylenko on Tuesday said on Ukrainian TV that Russian shelling there over the previous day killed one civilian and wounded another.

During a visit to the Lima, Ohio, tank plant in February, Army Secretary Christine Wormuth met with officials there at length to determine the best options for getting the tanks to Ukraine.

“Part of it is figuring out — among the different options — what’s the best one that can allow us to get the Ukrainians tanks in as timely a fashion as we can,” without disrupting foreign military sales, Wormuth said at the time.

Officials at the plant, which is owned by the Army and operated by Reston, Virginia-based General Dynamics, said production totals can vary, based on contract demands. And while they are currently building 15-20 armored vehicles per month, including tanks, they can easily boost that to 33 a month and could add another shift of workers and build even more if needed.

Development of tanks for Ukraine would have to be squeezed in between the current contracts for foreign sales, which include 250 of the newest versions for Poland and about 75 for Australia. During Wormuth’s tour of the facility, workers were preparing to build an updated version of the vehicle for Poland.

Ukrainian leaders have persistently pressed for the Abrams, which first deployed to war in 1991 and has thick armor, a 120 mm main gun, armor-piercing capabilities and advanced targeting systems. It runs on thick tracked wheels and has a 1,500-horsepower turbine engine with a top speed of about 42 miles per hour (68 kilometers per hour).