"Ukraine's ambassador to Germany, Andrij Melnyk, in an interview with Deutschlandfunk in Germany said: "Kyiv may consider building a nuclear weapon to counter Russia if it does not join NATO."
"Ukraine must either be part of NATO or the only option for it is to strengthen its weaponry options, including considering nuclear weapons," Melnik said.
Russia-Ukraine relations have deteriorated in recent weeks.
The two countries have repeatedly accused each other of escalating tensions in the Donbas region in eastern Ukraine.
Ukraine has accused Russia of sending troops to the border, Moscow, meanwhile, says its military moves are in response to Kyiv's provocative actions.
The West, meanwhile, is backing Ukraine.
Last week, Ukrainian Defense Minister Andriy Taran called on the European Union to support Ukraine against Russia.
Ukraine has recently received hundreds of millions of dollars in US military aid, including armored vehicles, UAVs and anti-tank missiles, and is stockpiling them near the Russian border.