Washington’s threat to leave the Open Skies Treaty, a pact allowing countries to conduct surveillance flights over each other’s territory, has left Europeans concerned that yet another landmark arms control accord might suffer the same fate as the Intermediate-Nuclear Forces (INF) Treaty.

The Open Skies Treaty, signed in Helsinki in 1992 and in force since 2002, covers 34 countries and is designed to build trust between signatories, allowing them to conduct short-notice unarmed surveillance flights to gather information on each other’s military forces, thereby contributing to inspections of conventional arms control and strategic offensive weapons and reducing the risk of conflict.

The accord provides all signatories with permanent access to unclassified and verifiable imagery received during observation flights relevant to their national security.

Russia and the United States, the world’s two biggest nuclear powers, have used it to keep an eye on each other’s activities, but in recent months several senior US Democratic lawmakers and non-proliferation experts have warned that they believe US President Donald Trump may pull Washington out of the pact.

Earlier this year, the Trump administration withdrew the US from the UN’s Arms Trade Treaty (ATT), an international arms sales agreement.

It also terminated its participation in the INF with Russia that banned ground-based, medium-range nuclear missiles, effectively killing the treaty.

The last remaining major nuclear arms control treaty between the United States and Russia, New START, is due to expire in February 2021 and Moscow has already warned there is not enough time left to negotiate a full-fledged replacement.

Experts now fear that a potential US exit from the accord would further erode the global arms control architecture which is under pressure since the INF’s demise in August.

“The Trump administration has already laid waste to several international agreements designed to enhance the security of the United States and its allies and it appears the Open Skies Treaty could be next on the kill list,” Kingston Reif, Director for disarmament and threat reduction policy at Arms Control Association, told EURACTIV.

“Treaty flights, including over Russia, strengthen ties between the United States and its allies and reassure non-NATO members on Russia’s periphery,” Reif said.

“Withdrawing from the treaty would be another step in the collapse of US leadership and further alienate US allies and partners,” Reif added.

Asked what the cancellation of yet another arms control treaty could mean for European security, Reif said “the worst case scenario would be the United States withdrawing from the treaty without the support of its allies, which would deprive Washington of flying over or participating in flights over Russia, while Russia would still be able to fly over US military assets in Europe.”

According to a report by DefenseNews, during a visit in Brussels in November Trump administration officials laid out for the first time a full suite of concerns with the treaty and made clear they were seriously considering exiting it, presenting NATO allies with classified intelligence suggesting that Russian forces are “misusing the treaty in their targeting of critical US infrastructure.”

Critics of the accord have complained that Moscow in the past has tactically restricts flights near the Russian exclave of Kaliningrad and the Georgian border-conflict regions of South Ossetia and Abkhazia, to which the US responded with flight restrictions over parts of Hawaii and Alaska.

Reacting to the withdrawal discussion, senior Russian Foreign Ministry officials have announced that Moscow has already drawn up retaliatory measures in case the US leaves the Open Skies treaty, the RIA news agency reported in November.

“Of course. We’ve got everything ready. You’ll find out,” Vladimir Ermakov, head of the ministry’s arms control and non-proliferation department, was quoted as saying.

NATO officials have reacted cautiously to the situation, but repeat that the treaty is “an important tool for military transparency and predictability”.

Nevertheless, European reactions have been largely negative, as they face the threat to lose one of their most useful control instruments in their relations with Russia. According to security sources, several high-ranking European security officials have reportedly asked Washington for an explanation of its intentions.

Scandinavians, particularly military neutral Sweden, have tried to influence the US position with a letter to US Secretary of Defense, Mark Esper, while the UK, France and Germany wrote a joint démarche.

An EU spokesperson confirmed to EURACTIV that Brussels is aware of the withdrawal debate.

“The Treaty on Open Skies has served as an important confidence and security-building measure in the OSCE area, providing transparency and predictability in the politico-military dimension of European security,” the EU spokesperson said.

“We hope that all State Parties continue to recognise the contributions of the Treaty to European and global stability,” she added.

In the OSCE area, Ukraine has a vital interest in maintaining the treaty as it “contributes significantly to the achievement of the OSCE’s objectives, especially as regards the implementation of confidence-building and security measures in Europe,” the Mission of Ukraine to the EU told EURACTIV in a statement.

Asked what effect its termination could have on the security situation in Ukraine, arms control expert Reif told EURACTIV that the surveillance flights over Ukraine and western Russia “have yielded valuable data and has been a useful tool in helping to counter Russia’s aggression against Ukraine”.

In addition to the usual quota observation flights, since 2014 and the start of the war in eastern Ukraine, Western European treaty signatories have completed a number of so-called “extraordinary observation missions” under the accord over Ukrainian territory.

One such example occurred in December 2018, when the United States together with Canadian, French, German, Romanian, British and Ukrainian observers, conducted an “extraordinary flight” under the treaty over eastern Ukrainian territory after a Russian attack on Ukrainian naval vessels in the Black Sea. After the surveillance flight, the US Department of Defense issued a statement stating that “the timing of this flight was intended to reaffirm US commitment to Ukraine and other partner nations”, while the Ukrainian Foreign Ministry added in a similar statement the country would be “interested in maintaining and implementing the treaty”.

Similar flights have since taken place with the aim of monitoring the security situation in the area.

During the Open Skies Consultative Commission meeting at the OSCE Headquarters in October, a decision was made on the distribution of active quotas for observation flights in 2020.

According to sources participating in the meeting, the decision was taken by all participants without reservations, including the US side, which has not specified its intentions of potential withdrawal.

“Ukraine is actively working to prepare for the implementation of the Open Skies Consultative Commission’s decision in 2020,” the Kyiv Mission to the EU told EURACTIV.

[Edited by Benjamin Fox]