BRUSSELS — NATO on Tuesday reinforced its defenses against Russia from the Baltic to the Black Sea, delivering what its chief called a clear message to Moscow that ‘‘if any of our allies is attacked the whole alliance will respond as one.’’

Jens Stoltenberg, secretary-general, said NATO defense ministers agreed to deploy four multinational battalions on a rotational basis to Estonia, Latvia, Lithuania, and Poland. They also agreed on ‘‘tailored measures’’ to enhance ‘‘defense and deterrence’’ in the Black Sea region, including the advance stockpiling of equipment and supplies.

‘‘NATO is an alliance that delivers,’’ Stoltenberg said.

Earlier, he called ‘‘defending our territory and protecting our people’’ NATO’s primary task.

The ministers’ meetings are meant to set the stage for NATO’s July 8-9 summit in Warsaw. On Tuesday and Wednesday, ministers are also expected to agree to cooperate more closely with the European Union in security affairs and meet with Ukraine’s defense minister.

Without disclosing details, Stoltenberg said ‘‘we will establish a framework to deal with threats and challenges from the south’’ — NATO-speak for the Islamic extremist violence in the Middle East and North Africa.

The United States, Britain, and Germany are committed to spearheading development of three of the four battalions. A senior US official said Canadian leaders are discussing the possibility they would coordinate development of the fourth.

Associated Press