President Donald Trump has proposed a 10 percent cut to a critical fund serving as a bulwark against Russian aggression in Europe, according to Defense Department documents, at a time when U.S. and allied officials are concerned their efforts to counter Moscow are insufficient.

The Pentagon's proposal for next year's budget, released Tuesday, reduces the European Deterrence Initiative from $6.5 billion last year to $5.9 billion – one of the few funds for overseas operations seeing a proposed cut. The fund, originally called the European Reassurance Initiative, began during the Obama administration in response to Russia's annexation of the Crimean Peninsula and its ongoing support for separatist rebels in Ukraine's eastern reaches.

The initiative supports American and allied operations in other parts of Europe to deter Russian aggression, including battalions of troops in Poland and the Baltic states. Leaders in those countries and Russia hawks at home consider it an integral component to containing Russia's recent expansionist behavior.

And it comes at a time when American officials question whether they have sufficient resources in Europe to counter Russia.

"I'm not comfortable yet with the deterrent posture we have in Europe," Army Gen. Curtis Scaparrotti, the outgoing head of U.S. European Command and top officer for NATO, told a congressional panel last week, citing the need for more air-, land- and sea-based forces.

Throughout his presidency, Trump has questioned the need for alliances like NATO and repeatedly called on allied countries to do more for themselves. The Pentagon echoed the latter priority Tuesday.

When asked about the cuts, the Pentagon's top finance official said, "We are continuing to be committed to our NATO partnership."

"We're very much preparing for great power competition," Deputy Under Secretary of Defense (Comptroller) Elaine A. McCusker told reporters, citing the Pentagon's latest strategy. Investments in more troops and equipment last year are followed by more exercises this year, she said.

"We're also looking at increased burden-sharing," McCusker added.

Despite the call for broad cuts, the specific fund designed to provide weapons to the Ukrainian military is not affected in the proposal. Known as the Ukraine Security Assistance Initiative, or USAI, Trump's proposed budget maintains funding levels at $250 million to "provide assistance and support to the military and national security forces of Ukraine" and to replace weapons or other military gear.

The notion of providing Ukraine with lethal weaponry has been a contentious issue and one the Obama administration refused to do for fears it could escalate a conflict with Russia. Trump in 2017 approved the deployment of Javelin anti-tank missiles, which were delivered to the Ukrainian military last year. Congress has mandated that the money to Ukraine should include lethal weaponry.

Scaparrotti told Congress last week he is considering other weapons the U.S. could supply to Ukraine, including to bolster its sniper capabilities and to prevent another crisis like the one that took place in the strategically critical Azov Sea last year.

Other funds for foreign combat operations, known as the Overseas Contingency Operations budget, are increased in the proposal, including $100 million more for the war in Afghanistan and $1.6 billion for broader support missions around the globe. The budget for the war against the Islamic State group is slated to be cut by $2 billion as the U.S. nears the completion of the militate campaign against its so-called caliphate.

