The European Union has called on Russia to take steps to de-escalate the situation in Ukraine, EU High Representative for Foreign Affairs and Security Policy Catherine Ashton said in Brussels on Thursday.

"The EU will not recognize the annexation of Crimea by Russia," she said, while delivering her report at an annual conference on European defense organized by the European Defense Agency (EDA).

Ashton noted that this year's EDA conference "takes place against the backdrop of the most tense situation in our neighborhood since the end of the Cold War."

"We will continue to engage and use all diplomatic and political means to stabilize the situation and prepare the ground for a genuine political solution," she said.

She said that the EU and its member states were working hard "to help ensure a viable and sustainable economic future for Ukraine" and "stabilize the country and its institutions in these crucial days."

She said that the EU's response had been measured, but determined.

"We have also been clear that any further escalation would lead to concrete and serious economic sanctions," Ashton said.

She recalled that this issue was discussed at the EU-U.S. summit on March 26 and that the sides had agreed to continue consultations and coordinate actions on this issue.

Ashton said that "the events of these last weeks remind us that peace and stability in Europe could be more fragile than we all would hope."

She said that Russia's unilateral action "can call into question four decades of confidence building and developing shared principles in Europe."

"We need to take time and reflect on what this means for the EU: what we can do to prevent such situations, how we can best respond to them and how we need to organize and equip ourselves in a rapidly changing strategic and geopolitical environment," Ashton said.

In her opinion, defense matters for a number of reasons, "but recent events remind us that it matters first and foremost because it provides security to our citizens."

Ashton noted that one of the EU's most valuable instruments and greatest strengths was the comprehensive approach.

"It is about the effective combination of diplomatic, military, political, financial and other instruments. But most of all it is about the broadest possible vision of what security is about," she said.

In this respect, she noted that comprehensiveness means investing in early warning, being prepared and conflict prevention just as much as in crisis response, stabilization and peace-building, development and policy dialogue.

"It also means to systematically and closely work with partners on the full range of issues that may pose security risks," Ashton said.