Germany and nine other nations took the next stage in their efforts on Wednesday to jointly purchase air defense systems such as Patriot, IRIS-T, and Arrow 3 as NATO allies hurry to fill gaps left by Russia’s conflict on Ukraine.

Belgium, Czechia, Denmark, Estonia, Hungary, Lithuania, and the Netherlands signed an agreement on the margins of NATO’s Brussels headquarters to lay the legal groundwork for future purchases.

Together with Germany, Slovenia and Latvia, who signed up earlier, they make up a group of ten countries that aims to spearhead joint procurement within the wider German-led, 19-nation European Sky Shield Initiative.

German Defence Minister Boris Pistorius said he expected the first deals to be struck within three to four months.

Ground-based air defence systems such as Raytheon’s (RTX.N) Patriot or IRIS-T, which is produced by German arms maker Diehl, are built to intercept incoming missiles.

After the Cold War, many NATO allies scaled down the number of air defence units to reflect their assessment that they faced only a limited missile threat, from countries such as Iran.

This perception changed drastically with Russia’s invasion last year of Ukraine, which sent NATO allies scrambling to tackle air defence shortfalls while at the same time supplying Kyiv with the coveted systems.

Set up one year ago, the European Sky Shield Initiative groups 19 nations including Britain, the Baltic states and several eastern European countries who aim to buy air defences mainly off the shelf instead of developing new systems, to cut down on procurement times.

With the move, Germany upset France, which favours the development of European systems and has declined to join the initiative. France has said the initiative creates new dependencies on the countries and companies that make the defence systems.