ABOARD A US AIR FORCE AIRCRAFT ABOVE EUROPE — Dozens of US diplomats and senior military leaders from throughout Europe are gathering for a meeting Friday morning in Stuttgart, Germany, to analyze America's handling of Russia over the last 18 months.

The meeting, led by US Defense Secretary Ash Carter, will tackle a number of issues facing the US in Europe, but will spend significant time analyzing and developing strategy for how to handle the ongoing conflict between Russia and Ukraine, as well as concerns from regional allies that Russian Prime Minister Vladimir Putin may look to expand his territory elsewhere.

"Secretary Carter looks forward tomorrow to meeting with his senior military leaders and representatives from the State Department to discuss a range of issues facing the United States in Europe," Pentagon spokesman Brent Colburn said.

"This meeting is intended to inform the secretary's thinking as he heads into his first NATO ministerial in late June," Colburn continued. "One of the areas of focus will be Russia's actions over the past 18 months, including their operations in Ukraine."

A senior defense official, briefing reporters on background en route to Germany from New Delhi, said the idea is to analyze whether the US response to Russia's invasion of Ukrainian territory has been appropriate and where it can be improved. That includes whether new reassurance measures are needed to calm allies who are warily eyeing Russia.

The official highlighted the inclusion of State Department officials as setting this meeting apart from other strategy sessions. Those State representatives will help convey that sentiment inside countries where they are stationed, and give the Pentagon a clearer sense of how to reassure those nations. They can also "make sure the political will is still in place for key European partners to keep sanctions in place and keep the pressure on Russia," the official said.

"You'll very often hear the secretary say that military options in this context are one part, but not the more important part" of the US strategy, the official said. "[Carter] believes very strongly that the economic sanctions are the most important part of putting leverage on Russia right now."

The event is part of Carter's prep ahead of a series of major European meetings, including the annual NATO ministerial talks, a meeting of the G-7 and one of the Council of Europe.

"We do expect other NATO issues will come up," the official said. "We expect discussion of ISIL, some discussion of the southern flank of NATO. That's all part of the mix."

During the confirmation hearing for Carter, he did not close the option of directly arming Ukraine. Asked whether that would be discussed at the meeting, the official said Carter's "position on that has not changed, and that's something that we continue to assess."

At the NATO summit later this month, Carter will be discussing the European partners' commitment to military spending. While some European nations, such as Poland, have increased their defense spending, others are drawing down significantly.

Asked whether Carter will call for greater defense spending from European partners during his NATO visit, the official said, "You should definitely expect that."

Twitter: @AaronMehta