(Reuters) - Russia's Foreign Minister Sergei Lavrov said on Monday that U.S.-built F-16 fighter jets can 'accommodate' nuclear weapons and warned that supplying Kyiv with them will escalate the conflict further.

"We must keep in mind that one of the modifications of the F-16 can 'accommodate' nuclear weapons," Lavrov said in a speech at a military base in Dushanbe in Tajikistan, according to a transcript on the ministry's website.

"If they do not understand this, then they are worthless as military strategists and planners."

Ukraine's President Volodymyr Zelenskiy has long appealed for the F-16 jets, saying their appearance with Ukrainian pilots would be a sure signal from the world that Russia's invasion would end in defeat

U.S. President Joe Biden told G7 leaders last month that Washington supported joint allied training programmes for Ukrainian pilots on F-16 fighters.

But U.S. National Security adviser Jake Sullivan said there was no final decision on Washington sending aircraft.

(Reporting by Lidia Kelly in Melbourne; Editing by Michael Perry)