Story highlights General Joseph Dunford is the chairman of the Joint Chiefs of Staff

Dunford is expected to issue a note to all military forces as soon as this week telling them to stay out of politics

(CNN) Growing concern that top U.S. military leaders are increasingly being asked to comment on proposals by presidential candidates has led the chairman of the Joint Chiefs of Staff to draft a letter to all troops with one message: Stay out of politics.

Gen. Joseph Dunford is expected to issue a note to all military forces as soon as this week.

Dunford will "remind the troops of the need to remain apolitical in order to sustain Americans' trust and confidence in them," said the chairman's spokesman, Capt. Gregory Hicks.

The U.S. military has a longstanding tradition of remaining out of politics so that commanders are free to give any president their best military advice without it being seen as part of a political agenda.

Hicks noted that the issue often comes up during the presidential campaign season. Troops are reminded not to appear in uniform at political events, for example.

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