Romania, a NATO member since 2004, shares a 650-km (400-mile) border with Ukraine and has had Russian drone fragments stray into its territory repeatedly as Moscow attacks Ukrainian ports just across the Danube River.

The government sent the law to parliament for approval on Monday.

Once President Klaus Iohannis signs the bill into law, the government will issue an order for the donation to go ahead.

Romania decided to donate one of its two operational Patriot systems - one of five such systems and other strategic air defense units pledged by NATO states to Kyiv - on condition that allies replace it with another Patriot system at a later date.

The draft law parliament approved states the replacement Patriot system from the United States should not cost more than Romania originally paid per unit, and that the costs will be covered from "non-refundable foreign sources".

Romania signed a $4 billion deal to buy Patriots in 2017, its biggest procurement contract to date. It has received four systems so far, with two operational.