Traders assign a 95.3% probability against Ukraine joining NATO before 2027 due to the ongoing conflict with Russia, which creates acute risks under Article 5 collective defense obligations for all alliance members. NATO has maintained an open-door policy and provided security assistance, yet accession requires unanimous ratification by current members, including those with longstanding reservations over governance reforms and border disputes. Recent alliance summits have prioritized training programs and equipment deliveries without setting firm timelines, underscoring the structural hurdles. A rapid ceasefire agreement or unexpected diplomatic realignment among key capitals could still shift momentum, though such developments remain constrained by entrenched positions on both sides.