Writing in the Financial Times, U.S. presidential candidate John McCain (pictured) explains "why we must be firm with Russia." Referring us to the article, reader Jeremy Putley notes that unfortunately McCaine totally omits reference to Russia's horrendous crimes in Chechnya, but commends McCain for making "a good start."

In perhaps the most direct challenge by any nation to Euro-Atlantic security since the end of the cold war, President Vladimir Putin has threatened to target European capitals with nuclear weapons and veto a United Nations resolution on the status of Kosovo – the culmination of 15 years of effort by the international community to create a lasting foundation for peace in the Balkans. Russia has also threatened to withdraw from the treaties limiting nuclear and conventional force deployments in Europe. Moscow refuses to extradite a Russian agent accused in a British court of assassinating a Kremlin political opponent in London.

During the past four years, many independent Russian journalists have been murdered in mysterious circumstances, including the renowned Anna Politkovskaya. The state now owns nearly all broadcast media in Russia. Political dissent has been silenced. The Russian government has overseen the largest state-directed seizure of private wealth and foreign investment since the 1930s. The government is accused of launching a cyberwar against Estonia and has used energy as a weapon against smaller neighbours. Mr Putin has called for a new international order that would elevate authoritarian states such as Russia, China and Iran at the expense of the western democracies.

Mr Putin recently summed up these dubious accomplishments by describing himself as the world's greatest democrat since Mahatma Gandhi. His blend of cynicism and Napoleonic delusion presents a dangerous challenge to the Euro-Atlantic community. A profoundly authoritarian regime, dominated by an intelligence service hostile to western liberal values and flush with cash from oil and gas, holds power in Moscow. This development calls for a new western approach to a revanchist Russia, grounded in our shared strength as liberal democracies.

Clearly, we in the west must pursue co-operation with Moscow where we can. But too many believe that we can define an agenda of co-operation that is divorced from the nature of the Russian regime and its actions against its own citizens. It is not possible to separate the character of Russian foreign policy from the assault on fundamental freedoms in Russia itself, because they spring from the same source.

Mr Putin's threats to target population centres in Europe with nuclear warheads reflect a startling disregard for human security that characterises the Russian government's approach to its own people. Moscow's meddling in Ukrainian politics and sponsorship of armed secessionists in Georgia and Moldova subverts governments freely elected by their citizens.

The influence of Russia's security services at home is mirrored in Russian foreign policy: American and British authorities confirm that the number of Russian intelligence agents operating in their capitals has reached cold war levels. Russian obstruction of international efforts to resolve the Iranian nuclear crisis and end genocide in Darfur emboldens authoritarian leaders in Tehran and Khartoum to remain defiant, paralleling Russia's own lawless behaviour at home and abroad.

To meet the challenge of Russian revanchism, the world's liberal powers could agree to form a League of Democracies to address challenges such as Iran and Darfur where authoritarian veto-threats prevent effective action to uphold shared liberal values. Western leaders could agree to return the Group of Eight to its roots as the club of leading market democracies, which does not include Russia.

Rather than tolerate Russian nuclear blackmail or cyber-attack, western nations could make clear that Nato solidarity is indivisible and that its doors remain open to all democracies committed to the defence of freedom – regardless of Russian fulminations.

Europe and the US could also pursue German chancellor Angela Merkel's bold suggestion to construct a transatlantic marketplace and invite Russia to join when it meets benchmarks on rule of law and economic freedom. The European Union could develop a shared energy policy to govern Russian oil and gas imports, and provide energy security for import-dependent economies. We must all step up our programmes to support fundamental freedoms and the rule of law in Russia, rather than cutting them back as is proposed in the US. We should expand our scholarship and exchange programmes to build ties with a new generation of Russian leaders.

In a famous essay in 1947, George Kennan wrote that Russia's external behaviour was a product of the Russian political system, but that a firm western response to Soviet aggression would eventually bring about the mellowing of the regime that produced it.

Russia today is not the adversary it was then, partly because it decided to end the cold war and reconcile with the west. It now appears to be going its own way. A firm and unified response by the world's great democracies to aggressive Russian behaviour abroad could mellow the belligerent elements in Moscow's political system, illuminating for Russia's leaders a pathway of democratic co-operation that writes a new chapter of Russian history, rather than reopening an old one.