There are informal agreements between NATO countries to refrain from supplying certain types of weapons to Ukraine.
According to the German news agency DPA, this is due to the risk of a direct military confrontation with Russia, which the Alliance wants to minimize.
There are fears that Russia may officially consider the supply of Western tanks and combat aircraft as NATO entering the war and take military measures in response. Weapons systems of this type have not yet been supplied to Ukraine.
According to the parliamentary group of the Social Democratic Party of Germany (SPD), German government is fully aware of this informal agreement.
"The Defence Committee was fully informed of this in mid-May," the SPD Defense spokesperson Wolfgang Helmich told the DPA.
According to him, all decisions on weapons supplies, are ultimately made by individual member countries. So far, they have stuck to informal arrangements, considering that they may not receive the full support of their NATO partners in the event of a Russian attack.
For this reason, more than two months ago, Poland refrained from supplying Soviet MiG-29 fighters to Ukraine, the agency notes.
Tod Daniel Walters, the commander-in-chief of U.S. Armed Forces in Europe, said in March that the MiG-29 deliveries were a "high-risk scenario" because they could be misjudged by Moscow and lead to an escalation between Russia and NATO.
And French President Emmanuel Macron said after a special NATO summit on arms shipments: "There is a limit, which is not to become a party to war."