Dean Rusk was Secretary of State from 1961 to 1968, under Kennedy and Johnson. He was one of the most experienced senior officials regarding Vietnam, having worked as assistant secretary of state for Far Eastern Affair in the 1950s.

Rusk was one of the "hawks" of the administration, and he consistently pushed for tougher and deeper American involvement. In spite of his record, in 1965 he favored a bombing halt, albeit more as a public relations stunt that as a real diplomatic overture. Again in 1968, Rusk argued in favor of some restraint in the bombing of North Vietnam to allow room for negotiations.

Excerpts from Rusk-McNamara Report to Kennedy, November 11, 1961
From the Vietnam Wars Page at Vassar College
http://vietnam.vassar.edu/~vietnam/doc7.html

After their assessment trip to Vietnam, Rusk and Secretary of Defense McNamara wrote this report for Kennedy. McNamara and Rusk recommended a boost to U.S. military presence "...required for increased United States participation in the direction and control of GVN military operations."

Memorandum to the President on the Legal Basis for Sending American Forces to Vietnam
From the Historian of the State Department
http://www.state.gov/www/about_state/history/vol_i/226_254.html (Doc #226)

At Johnson's request, Rusk sent him this legal justification of the deployment of U.S. combat troops in Vietnam, both from an international and a domestic point of view.

The U.S. State Department on North Vietnam's Aggression
From the Modern History Sourcebook at Fordham University
http://www.fordham.edu/halsall/mod/USStateDept-vietnamfeb1965.html

The U.S. Department of State Bulletin published this statement in March 1965 insisting that the war in South Vietnam was not a civil war, but an aggression on a sovereign country not unlike Korea.