Switzerland said on Friday it has rejected a request from Madrid to allow Spain to re-export Swiss-made anti-aircraft guns to Ukraine.
Spain made the request in January to allow it to send two 35mm anti-aircraft guns to Ukraine.
Switzerland has previously vetoed requests from Denmark and Germany who wanted to send Swiss-made armoured vehicles and ammunition to help Ukraine in its war against Russia.
Switzerland's War Materials Act does not allow the export of war materials if the destination country is involved in an internal or international armed conflict.
However, the issue of weapons deployment is becoming a sensitive topic in neutral Switzerland, with the population increasingly in favour of the current restrictions being lifted.
Politicians have also launched a campaign for the law to be altered, with the issue being discussed by parliament.
"Spain's request for a waiver of the non-re-export obligation was examined in the light of the same criteria as an export of war material from Switzerland," the government said on Friday.
"The requests were therefore answered in the negative."
(Reporting by John Revill; Editing by Toby Chopra and Susan Fenton)