( CNN ) -- Twenty years ago this month , Ukraine , Russia , the United Kingdom and the United States signed an agreement that represented a major step in global anti-proliferation efforts . Under the deal , known as the Budapest Memorandum , Ukraine voluntarily surrendered the third largest nuclear arsenal in the world , which it had inherited after the collapse of the Soviet Union . But fast forward two decades , and an agreement once heralded as a breakthrough is gradually being undermined by one of the very countries that signed it . As part of the agreement , Ukraine willingly gave up more than 1,000 strategic and 2,500 tactical nuclear weapons , and agreed to the destruction of 176 silos used to launch intercontinental ballistic missiles . In return , Ukraine was offered security assurances by Russia , the United Kingdom and the United States in a document that highlighted the inviolability of Ukraine 's existing borders and its sovereignty , called for the abstention from forceful actions that could threaten Ukraine 's territorial integrity and prohibited economic pressure being placed on Ukraine . Unfortunately , Russia has disregarded each of these provisions . Russian aggression against Ukraine , first in Crimea and soon after in eastern regions of Ukraine , has created an unprecedented challenge to international peace . Indeed , rather than simply being a domestic or even regional crisis , what has been unfolding this year constitutes a violation of international law , undermining the existing checks and balances of the international system . For many years , the Budapest Memorandum served as a practical model for the implementation of the international nonproliferation regime . But recent violations of the agreement now risk undermining a system that safeguards states against national security threats through diplomatic means . As a result , many states may start to view the possession of weapons of mass destruction as the only effective means of safeguarding against external risks , in the process provoking a new arms race and ultimately increasing the threat of nuclear disaster down the road . None of this is to suggest that Ukraine is not grateful for the effort behind the memorandum ; other nations offered decisive support for our country 's independence . More recently , there has undoubtedly been practical assistance in our efforts at countering Russian aggression , and the United States and United Kingdom have both remained reliable and virtuous partners on the international stage . And yet , despite this assistance , it has become increasingly clear that the power of the Budapest Memorandum to guarantee our national security has taken a hit . It is that realization that has prompted Ukraine in recent months to push for closer integration with NATO , a cause that is popular both with the Ukrainian people and which is also gaining political support . As President Petro Poroshenko noted last month , `` it is clear that the non-bloc status of Ukraine proclaimed in 2010 could n't guarantee our security and territorial integrity . ... This position has led to serious losses . That 's why we 've decided to return to the course of Euro-Atlantic integration . '' There is , of course , much work to be done if we are to reach the alliance 's compatibility standards , which is why the government has formulated a six-year plan for meeting membership requirements . But in the end , it seems only fitting that the status of Ukraine 's relationship with NATO be left to the Ukrainian people , and any decision in this regard will only be taken after consulting them in a form of referendum . More broadly , recent events in Ukraine have underscored the need for a rethink of the existing global security architecture . And while Russian aggression is clearly the catalyst , any changes should not be seen as simply directed at a single country , but as part of generally much-needed changes . It is imperative in our fast-changing world that states are granted new means of defending their territory , and that the most effective mechanisms are in place for preserving international peace . It 's a conversation that Ukraine , now more than ever , is keen to take part in .
Ambassador : Russian aggression against Ukraine has been challenge to Ukraine . Olexander Motsyk : Ukraine has violated terms of Budapest Memorandum . Time for Ukraine to rethink relationship with Russia , he says .