If automatic budget cuts known as sequestration take effect at the beginning of March, the Navy would be forced to halt all deployments to South America and the Caribbean and limit deployments to Europe to just ships supporting ballistic missile defense missions, the Navy’s top officer warned in a recent memorandum.

Adm. Jonathan Greenert, the Chief of Naval Operations, wrote in an internal Jan. 25 memo that the service would face more than $4 billion in additional cuts to the operation and maintenance (OMN) accounts that would require the Navy to scale back its activities and overseas presence.

“Absent the authority to reprogram (transfer) funds from other accounts to OMN, the Navy will be compelled to significantly reduce OMN expenditures through numerous actions,” Greenert said.

In additional to stopping and restricting planned deployments, the Navy would reduce the days at sea and flying hours across the entire force, cease stateside training, flying, steaming, and other operations “for the majority of ships and aircraft preparing to deploy” unless other funding means are found, he said.

As it is currently written, sequestration would impose automatic cuts across most Pentagon accounts without allowing budget officials to shift funding around to suit priorities. Congress avoided an initial threat of sequestration, which would have kicked in earlier this month, by delaying it by two months as part of a broader legislation package largely focused on taxes.

But Republicans and Democrats have yet to agree on a plan to permanently resolve sequestration, which was introduced in August 2011 and designed to leverage both parties into agreeing on a long- term federal spending reduction plan to curtail the nation’s ballooning debt and deficits.

Worsening the situation, Greenert said, is that Congress has yet to pass a defense appropriations bill for fiscal 2013. Instead, budgets are being governed by a continuing resolution (CR), which keeps spending levels at about the same amount as fiscal 2012. Because of the CR, Greenert warned the Navy will begin facing “significant additional budget reductions” in March.

The memo instructs fleet commanders by Feb. 15 to notify contractors and cancel all private sector surface ship maintenance availabilities for the final six months of fiscal 2013, which runs through September. CRs prohibit the Navy from beginning new maintenance work on ships.