BRUSSELS, June 25 (Xinhua) -- NATO Secretary General Jens Stoltenberg said that military mobility is a key area of NATO-EU cooperation ahead of a meeting with EU ministers on Monday.

Welcoming strengthened cooperation between the two blocs, Stoltenberg said that Presidents of the European Council and the European Commission will participate in the NATO summit in Brussels next month.

He noted that he will sign a joint declaration with EU leaders on the margins of the NATO summit, which will set out the visions for further cooperation.

Addressing the areas of NATO-EU cooperation, Stoltenberg said, "We need to be able to move forces quickly throughout Europe, when needed."

He noted that NATO has invested in projects supporting military mobility over the last four years, including upgrading harbor terminals and runways. "So we have already started to move but I welcome to do more together with the EU," he said.

The NATO chief also highlighted the coherence between capability developments of NATO and the EU, adding that the EU efforts on defense are "not competing but are complementary" to NATO.