WASHINGTON (AFP) - The Nato alliance faces a crisis as European countries have failed to invest in defence for years and grown averse to military force, US Defence Secretary Robert Gates said on Tuesday. A shortage of helicopters and cargo aircraft in the alliance was an example of chronically low levels of defence spending that had damaged the Nato-led mission in Afghanistan, Gates said. Right now, the alliance faces very serious, long-term, systemic problems, Gates said in a speech to alliance officers and officials. In a blunt message to allies as Nato-led forces face a tough fight in Afghanistan, Gates said a budget shortfall plaguing the North Atlantic Treaty Organisation represented a symptom of deeper problems with how Nato sets priorities and how European societies perceived the role of the military. The demilitarisation of Europe - where large swaths of the general public and political class are averse to military force and the risks that go with it - has gone from a blessing in the 20th century to an impediment to achieving real security and lasting peace in the 21st, Gates said. The perception of weakness among allies could offer a temptation to miscalculation and aggression by hostile states, he said. Funding and equipment shortfalls, meanwhile, complicated efforts to stage joint military operations in Afghanistan or elsewhere, he said. For many years, for example, we have been aware that Nato needs more cargo aircraft and more helicopters of all types - and yet we still dont have these capabilities, he said. The shortage of helicopters and cargo planes was directly impacting operations in Afghanistan. Nato also needed more aerial refuelling tankers and unmanned aircraft for surveillance and intelligence, he said. The US Defence Secretarys critical remarks came as Nato officials draft a new strategic vision for the alliance, which has struggled to redefine itself after the end of the Cold War. Gates, however, praised the alliance for its common effort in Afghanistan - where more than 120,000 troops were serving in the Nato-led force - and called on alliance leaders to show similar determination in pursuing reform. The challenge now is to bring that same level of commitment - that same willingness to make tough decisions - to institutional matters that are so critical to the long-term viability and credibility of Nato, and to the transatlantic security project writ large, he said.