WASHINGTON — The Pentagon’s watchdog agency has said the uncertainty of future funding specifically budgeted to reassure European allies against Russian aggression puts at risk the efforts meant to respond to crises in the region.

The U.S., NATO and Operation Atlantic Resolve countries are striving to gain interoperability and the capabilities required to counter threats in the area. And so in the past three fiscal years, the United States decided to provide extra Overseas Contingency Operations funding to bolster military activity in Europe after withdrawing troops and equipment in years prior as the military as a whole prepared to downsize.

When Russia annexed Crime in 2014, the U.S. and its NATO partners changed its strategy in order to reassure Eastern European countries along Russia’s border and to deter Russia from similar expansionist behavior in the future.

The European Reassurance Initiative, or ERI, funding more than quadrupled from FY15 to FY16, from $789 million to $3.4 billion. The FY18 request for ERI funding is $4.8 billion.

But since it’s funded like other wartime funding (on a yearly basis), the lack of predictability over how much will be allocated hurts the U.S. and NATO’s strategy, the agency said in a report evaluating ERI funding effectiveness released Tuesday. The rest of the Pentagon’s budget is planned on a five-year timeline.

“As a result, [U.S. European Command] and [Operation Atlantic Resolve] countries may be unable to sustain ERI’s contribution to allied and partner military capabilities,” the inspector general found.

According to the IG’s report, one chief of the comptroller division of a USEUCOM component command said it would be better to receive ERI funds through a mix of annual and multiyear allocations “to enhance predictability.”

And allied leaders said predictable funding would help long-term budget planning within their own countries. Poland, for instance, is planning its military budget for the next 10 years and needs “to understand long-range support requirements for U.S. forces,” the IG noted.

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Sustainability of ERI funding is also at risk due to planned personnel reductions in Europe.

“The influx of ERI funds and the related activities substantially increase USEUCOM headquarters and component requirements and activity levels,” according to the report. “However, U.S. forces’ staffing levels continue to decrease ... based on [the U.S. Department of Defense‘s] planned personnel reductions.”

The IG reported that senior USEUCOM leaders “highlighted to us the inconsistency between increased ERI requirements and fewer personnel available to execute them.”

The agency also expressed concern that the lack of predictability in funding could threaten infrastructure and readiness gains made through ERI funding in the past several years.

Yet, despite the funding, the IG found OAR countries “do not yet have sufficient procedures or transportation infrastructure in place to allow timely U.S., allied, and partner-nation military deployments.”

Over the course of the U.S. Army-led Saber Guardian exercise in July, Lt. Gen. Ben Hodges, the U.S. Army Europe commander, repeatedly stressed the importance of being able to rapidly move large numbers of troops and heavy equipment over large swaths of territory in Europe to be able to respond in a crisis.

U.S. and allied forces will be required to cross borders and use transportation infrastructure in the OAR countries, which means those countries and the U.S. will need to invest in improving the means by which militaries move. Hodges noted one way for NATO partners to reach their goal of spending 2 percent of gross domestic product on defense would be to invest in improving roads and railheads and help provide ammunition, ammunition storage and fuel.

“The challenges include lack of military movement agreements with other NATO countries, inadequate transportation infrastructure and related capability evaluations, and insufficient OAR country experience with planning and controlling military movement,” the IG stated.

ERI funding is going toward large training exercises like Saber Guardian to practice and iron out these movements as well as test the limits on maneuver capabilities across borders.

The U.S. has heavily invested, using ERI funding, in construction projects to improve military training facilities, airfields and weapons and ammunition storage.

Projects like these are further threatened by the lack of ERI funding predictability, the IG found, because construction projects aren’t typically budgeted on a yearly basis but are funded as multiyear projects.

The IG also found that USEUCOM doesn’t have metrics in place to accurately assess the impact of ERI funding on its strategy in Europe.

“This occurred because the existing USEUCOM-developed assessment processes do not isolate, and therefore cannot measure, the impact of the ERI separate from that of all other U.S.-funded support for training, infrastructure and capacity-building activities in NATO countries,” the IG stated.

Without a clear idea of the impact of ERI funding, “it is difficult for the DoD to measure OAR-country progress and to justify to Congress the need for additional resources required,” according to the agency.

Lastly, the agency said coordination and integration of ERI funding with NATO plans and capabilities “could be improved.”

OAR countries weren’t informed of key NATO deterrence training and programs planning details funded by ERI, according to the IG. For instance, the countries didn’t received advance notice of the Warsaw Summit 2016 decision to deploy NATO forces to the Baltic states and the relocation of U.S. forces from the Baltics and the Black Sea region to Poland in early 2017.