Since the Russian invasion first began more than a year ago, Ukraine has begged NATO member nations to supply it with more heavy weaponry, including combat fighter jets, though NATO and the broader West have been reluctant to do so -- until now, at least.

Poland announced on Thursday that it would send Ukraine four Soviet-era MiG-29 fighter jets "within the next few days," making it the first NATO nation to agree to do so, Reuters reported.

Polish President Andrzej Duda said in a news conference that the four MiG jets were in "full working order" and indicated that at least a dozen of the old Soviet-made aircraft would ultimately be transferred to Ukraine after the remainder were serviced and prepared for combat.

Poland and Slovakia to provide Ukraine with MiG-29s

The Associated Press reported that President Duda said of the MiG-29s, "They are in the last years of their functioning, but they are in good working condition."

The outlet noted that Poland, which was also the first NATO nation to provide Ukraine with the heavy tanks that it has also long sought, suggested in recent days that other member nations could soon follow suit in terms of providing combat fighter jets to the embattled country fending off a Russian invasion.

That prediction was prescient, as Time magazine reported that just one day after Poland announced that it would give Ukraine around a dozen MiG-29 jets, Slovakia announced that it would give Ukraine 13 of its own MiG-29s.

Slovakian Prime Minister Eduard Heger reportedly tweeted, "Promises must be kept & when @ZelenskyyUa asked for more #weapons incl. fighter jets, I said we’ll do our best."

So far, other NATO nations -- specifically Germany, the U.K., and the U.S. -- have been hesitant to provide Ukraine with fighter jets over concerns that doing so would be viewed by Russia as an escalatory provocation, but the recent move by Poland and Slovakia could prompt some reconsideration in that regard.

Ukrainian pilots already familiar with MiG platform

Time reported that Poland has around 28 old MiG-29s in its larger arsenal of around 94 combat aircraft -- which is primarily comprised of U.S.-built F-16 fighter jets -- and has said that it plans to replace the aircraft it will give to Ukraine with a combination of new South Korean-made FA-50 light fighter jets and U.S.-made F-35 stealth fighter jets.

The outlet further noted that the decision of Poland and Slovakia to give Ukraine some of their old Soviet-era MiG-29s, instead of the newer F-16s that Ukraine has requested, is because the Ukrainian Air Force already had dozens of MiG-29s of its own at the start of the conflict and its pilots are already familiar with and trained to operate the Soviet jets.

The transferred jets will likely be used primarily in a defensive capacity to intercept Russian fighter jets and bombers as well as cruise missiles.

They will also likely be put to use to provide close air support for Ukraine's ground forces in an upcoming planned counteroffensive against Russian-occupied positions.

U.S. still says no F-16s for Ukraine

Despite the likely increased pressure now on other NATO nations to follow the lead of Poland and Slovakia in providing combat fighter jets to Ukraine, CNN reported that President Joe Biden's White House remains resistant -- at least for now.

On Thursday, U.S. National Security Council spokesman John Kirby told reporters that Poland's decision "doesn’t change our calculus with respect to F-16s," and that, "These are sovereign decisions for any country to make and we respect those sovereign decisions."

"They get to determine not only what they’re going to give but how they’re going to characterize it," Kirby later added. "I wouldn’t think it’s our place to characterize Poland’s decision one way or another."

Decision could eventually change

The outlet noted that the decision of NATO nations to not provide Ukraine with F-16s is really just based on the practicality of the matter, given that it would take several months to retrain Ukrainian pilots to operate the more advanced U.S.-built aircraft, and particularly in light of the fact that those pilots were already familiar with and trained to operate the older Soviet-built jets.

That could potentially change going forward, however, as the Biden administration has already reversed course from its initial stance against providing Ukraine with heavy armor to eventually agree to give 31 M1 Abrams tanks plus an assortment of other more lightly armored vehicles to Ukraine.