WASHINGTON (AFNS) -- The Defense Department's nuclear deterrent is the ultimate protection for the United States while also assuring distant allies of their security against regional aggression, a senior Pentagon official told Congress March 7.

Elaine Bunn, the deputy assistant secretary of defense for nuclear and missile defense policy told the Senate Armed Services Committee's strategic forces subcommittee that while Defense Department modernization goals largely have not changed since 2010, some adjustments are on the horizon.

One such change, she reported, involves the new Strategic Arms Reduction Treaty force structure.

"The administration is considering how to reduce non-deployed strategic delivery vehicles to comply with the limits of the new START treaty by February 2018," she said. "And we will make a final force structure decision and inform Congress prior to the start of fiscal year 2015."

Bunn expressed concern about Russian activity that appears to be inconsistent with the Intermediate Range Nuclear Forces Treaty.

"We've raised the issue with Russia," she told the senators. "They provided an answer that was not satisfactory to us, and we told them that the issue is not closed."

With regard to recent ethical issues involving Air Force and Navy nuclear personnel, Bunn noted that Defense Secretary Chuck Hagel has created both internal and external special review panels.

"Those reviews are not about assigning blame," she said. "They're about identifying, assessing, and correcting any systemic deficiencies that we may uncover and in applying the best practices for carrying out our nuclear mission across the nuclear force."

Bunn also said the recently released 2014 Quadrennial Defense Review makes clear the key role of nuclear forces in the DOD strategy.

"It ... supports our ability to project power by communicating to potential nuclear-armed adversaries that they cannot escalate their way out of failed conventional aggression," Bunn said.

The department's budget request for fiscal 2015 supports DOD's nuclear policy goals as laid out in the 2010 nuclear posture review, in President Barack Obama's June 2013 nuclear employment strategy, and in the 2014 QDR, she added.

As a result, Bunn reported, Pentagon officials will continue to ensure that the current and future administrations have suitable options for deterring, responding to, and managing a diverse range of situations, including regional deterrence challenges.

"We continue to work closely with our allies, some of whom live in very dangerous neighborhoods, to ensure continuing confidence in our shared national security goals, including assurance of our extended nuclear deterrence commitments," she told the Senate panel.

Critical to maintaining a safe, secure and effective force is the preservation of the nuclear triad: strategic bombers, intercontinental ballistic missiles and submarine-launched ballistic missiles, Bunn said.