Late last month, GOP presidential frontrunner Donald Trump caused considerable controversy by arguing that the North Atlantic Treaty Organization was “obsolete” in dealing with the threat of terrorism and a drain on U.S. finances. Speaking to Jonathan Karl of ABC News, Trump also noted that the fate of Ukraine, which has strained relations between the United States and Russia, is not of vital national interest to the United States. “Ukraine is very far away from us,” Trump said and asked, “How come the countries near the Ukraine, surrounding the Ukraine, how come they’re not … at least protesting?”

Contrary to Trump’s assertions, Ukraine’s neighbors have been vocal in their opposition to Russian expansionism. Late last year, leaders of nine European countries met in Bucharest to express their concerns at Russia’s “continuing aggressive posturing.” Jointly, the leaders of Bulgaria, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania and Slovakia called for the creation of “a robust, credible and sustainable allied military presence in the region.”

But Trump’s comments, along with increasing financial strains in the United States and growing public weariness with regard to foreign entanglements, suggest that Eastern European countries, in particular, should not rely on NATO alone. Putting all of their eggs in the NATO basket could be dangerous and they should be thinking of an alternative.

Thoughtful leaders in Eastern Europe ought to ask themselves, how will NATO respond should Russia decide to invade, say, Estonia? A clear commitment from all 28 member states will be difficult to obtain. Some Western European states would presumably be much less willing to go to war against Russia on behalf of a distant Baltic state today than they might have been a generation ago, when the adversary was the Soviet Union and the threatened alliance partner was West Germany or the United Kingdom.

What about the United States? American conventional military power alone is arguably equal to that of the other 27 NATO members combined, and the United States also has a vast nuclear arsenal. But while the destructive power of America’s military cannot be seriously doubted, Washington’s willingness to wield it can be and should be. The United States, for example, might opt for stronger economic sanctions and eschew military confrontation with a nuclear-armed state — especially if war-weary Americans are dead set against initiating any new conflicts. In short, Putin cannot be certain of the U.S. response. But, neither can Estonia and other former Soviet bloc countries that Putin now threatens.

Given the questions surrounding NATO’s capacity for deterring Russian aggression, a more sensible course would strengthen military ties between the nine former Warsaw Pacts states currently in NATO, plus Ukraine, which isn’t. These countries could meet — say, in Warsaw, Poland — and hammer out a mutual defense treaty of their own. They might call it the New Warsaw Pact.

Ukraine is a vital component of this arrangement. Eastern European states, which do not want to border Russia, want to see Ukraine’s independence and territorial integrity preserved. They understand that if Russia is allowed to swallow additional parts or all of Ukraine (excepting Crimea, which is already gone), the former will become significantly more powerful, assertive and, consequently, dangerous. Putin too understands that bringing Ukraine into Russia’s orbit would enhance the latter’s power and be a key stepping stone toward reconstituting the Soviet Empire in some form. For its part, Ukrainian leaders understand that without economic and military reforms, the country might collapse. Thus, while currently weak, Ukraine is likely to become economically and militarily stronger in the future. As such, Ukraine is destined to be a large contributor of manpower and military spending to the New Warsaw Pact.

If such a pact became a reality, would it present a more effective deterrent than NATO?

First, the good news. On paper, the member states of the proposed pact are, collectively, comparable to Russia in isolation. Based on CIA World Fact Book estimates from July 2015, the New Warsaw Pact states’ combined population (143.9 million) is slightly greater than that of Russia (142.4 million). According to figures compiled by the World Bank, the combined GDP of the proposed pact is $1.5 trillion. Russia’s GDP is $1.9 trillion. That, however, is likely to shrink due to Russian over-reliance on the export of natural resources and the collapsing price of its major commodities.

Now, the bad news. Trump has a point when he criticizes the meager military spending of America’s NATO allies. The Stockholm International Peace Research Institute reports that Russia spent 5.4 percent of its GDP on its military in 2015. The new pact states spent 1.62 percent, on average, well below the NATO mandate of 2 percent. That amounts to annual military spending of $66 billion by Russia, versus a mere $22 billion by prospective pact members.

Moreover, the problems afflicting the NATO alliance would not go away altogether in a new, smaller pact. But it would be easier to sort out the member states’ true intentions, gauge the strength of their commitments to mutual defense, and resolve questions pertaining to military inter-operability and response time, in a ten-member alliance than NATO in its present form. Plus, the New Warsaw Pact would have a single clear goal: checking Russia. NATO does not have as clear a raison d’être.

While it is true that Article V could be invoked if Russia went to war with a NATO member, Eastern European countries, in particular, cannot be certain that it will be. A separate defensive alliance might provide greater reassurance to these most vulnerable states, and present a more credible deterrent to Russian aggression.

We are both children of the Cold War. One of us, Tupy, was born in Czechoslovakia, just eight years after Soviet tanks crushed the Prague Spring. No one who lived through that period could doubt that the Warsaw Pact was a symbol of occupation and humiliation. In short, we appreciate that the mere suggestion of resurrecting the Warsaw Pact may open old wounds.

But the countries of the former Warsaw Pact who are now members of NATO are subject to a different form of humiliation: that of being dependent upon others for their defense, including people many thousands of miles away who have not recently suffered under foreign occupation.

The mere fact that a leading contender for the Republican nomination has dared suggest that NATO has become irrelevant surely must give some in Europe pause. And, for the countries in closest proximity to Russia, even the possibility that some future American politician might share Trump’s nativist impulses, and casually discard the promises of past presidents, must be deeply unsettling. We shouldn’t be surprised if they hedge their bets, and create alternative means for defense that don’t hinge on the vagaries of American politics.

Christopher Preble is vice president for defense and foreign policy studies, and Marian Tupy is a senior policy analyst, at the Cato Institute.

Photo credit: Sgt. Anthony Jones, U.S. Army