The US Senate approved on Wednesday Finland and Sweden joining the North Atlantic Treaty Organization (NATO), the biggest expansion of the 30-member alliance since the 1990s, in response to Russia's war in Ukraine.

While voting was still going on in the 100-member council, the number of votes in favor was 83 to one against, easily exceeding the two-thirds majority, 67 votes, required to support ratification of the two countries' accession documents.

Sweden and Finland applied for NATO membership in response to Russia's months-long war on Ukraine, at a time when Moscow has repeatedly warned the two countries against joining the alliance.

NATO members signed the accession protocol for the two countries last month, allowing them to enter the US-led nuclear-armed alliance once member states ratify the resolution.

NATO Secretary General Jens Stoltenberg said at the time that the alliance shares with Sweden and Finland the same values ​​and challenges in facing what he described as the historical danger.

The accession must be ratified by the parliaments of all NATO member states before Finland and Sweden are protected under the Defense Clause, which states that an attack on one country in the alliance is an attack on all members.

It is noteworthy that Turkey (a member of NATO) agreed to launch this operation during the NATO leaders summit in Madrid last month, but Turkish President Recep Tayyip Erdogan reminded the two northern countries of the conditions to be achieved, in reference to the confrontation of organizations and personalities that Ankara classifies as terrorist entities.

On the other hand, the Kremlin said earlier that the Russian Defense Ministry is studying options for a response if NATO infrastructure is deployed near the Russian border after Sweden and Finland are included in the alliance.

Russian President Vladimir Putin has warned that Russia will have to respond in kind if military units and military infrastructure are deployed in the two countries, describing NATO as a tool of the Cold War and an expression of US foreign policy.