The Trump administration believes Russia's Su-57 stealth fighter and Tupolev PAK-DA stealth bomber will be developmental nuclear strike aircrafts.
The administration listed the two aircrafts as developmental nuclear strike aircrafts in its Nuclear Posture Review, a 100-page report released the first week of February 2018 laying out the U.S.'s nuclear policies.
The report took a harsh stance against Russia, saying that it "will pose insurmountable difficulties to any Russian strategy of aggression against the United States, its allies, or partners and ensure the credible prospect of unacceptably dire costs to the Russian leadership if it were to choose aggression."
The Su-57 first flew in 2010, but has yet to be mass produced.
Moscow announced on Feb. 7, 2018, that it would purchase about a dozen Su-57s this year, and receive two of those in 2019, according to TASS.
Nuclear strike delivery systems. (Nuclear Posture Review)
"We are taking the Su-57 for experimental and combat operation, and the state tests for the first stage are over," Russia's Deputy Defense Minister Yury Borisov told reporters, according to RIA Novosti.
The first batch of 12 will only be equipped with Saturn AL-41F1 engines — the same engines on the Su-35 — and not the new Izdelie-30 engines, which have only recently begun testing.
Russia's newly upgraded long-range bomber, the Tu-160M2, first flew January 2018, but the PAK-DA stealth bomber has yet to be built.
As such, Russia's main nuclear strike aircraft is currently the Su-34 Fullback, according to The National Interest.
"[Russia] has nuclear bombs for tactical aircraft and air launched tactical nuclear missiles as well. And there are ALCMs [air-launched cruise missiles] under development that will be used by tactical aircraft," Vasily Kashin, a fellow at Moscow's Higher School of Economics, told The National Interest.
"But I do not remember Su-57 being specifically mentioned," Kashin said, adding that it's possible that X-50 cruise missiles could fit into the Su-57's weapons bays. Russia, he said, has not confirmed anything.
Related: Russia's new Su-57 'stealth' fighter hasn't even been delivered yet — and it's already a disappointment
The status of the PAK-DA is even more up in the air.
Assuming Moscow builds the PAK-DA, it won't enter Russian service until the 2030s at the earliest, The National Interest reported.
The PAK-DA will probably be able to drop nuclear gravity bombs, according to The National Interest's David Majumdar. The aircraft will likely be primarily used as a strategic missile carrier — much like the upgraded Tu-160M2.
The Pentagon did not immediately respond to Business Insider's request for comment.