(VOVworld) - NATO chief Jens Stoltenberg pledged on Monday to expand the bloc's collective defense capability against any threats.

The secretary general said at the 62nd annual session of the NATO Parliamentary Assembly in Istanbul that NATO is considering boosting its collective defense, projecting stability, enhancing cooperation with the European Union, and strengthening the alliance by inviting Montenegro to become a member. NATO is taking steps to increase its presence in the Black Sea region and the eastern part of the bloc, including the deployment of four multinational battalions to the Baltic states and Poland. Stoltenberg added that NATO leaders are working on additional air and sea defensive measures.