As the French situation, at the battle of Dien Bien Phu, grew worse, they asked for U.S. air support; the proposed operation was called, in U.S. planning, Operation VULTURE. Its chief proponent, in the U.S. government, was the Chairman of the Joint Chiefs of Staff, Admiral Arthur D. Radford. French Gen. Paul Ely visited Radford in Washington, D.C., to make the request.
The proposal had no significant support with the other Joint Chiefs of Staff, the U.S. Department of State, or President Dwight D. Eisenhower. Their overall position, part of the broader geopolitical discussions in the main Dien Bien Phu article, was that they were reluctant to involve themselves in a colonial war on the Asian mainland, and that they would consider doing so only with a multinational force. Britain was extremely reluctant to join in such an operations, and Eisenhower eventually vetoed it.
There is serious question, however, how effective it might have been. In subsequent historical interviews, Vietnamese officers vary in their opinions. Some do suggest that it could have been a serious tactical problems, where others are much more confident that they could have worked around it, possibly delaying the eventual outcome.
On a practical basis, this was 1954, not 1968 when the electronics existed to bring heavy air support "danger close" to a base in a somewhat similar tactical position at the Battle of Khe Sanh.
Reports of Vulture planning differ as to whether the use of nuclear weapons was considered, although it is fairly clear that there would be extensive use of US B-29 heavy land-based bombers. Gen Earle Partridge, commanding US Far Eastern Air Force (FEAF), and BG Joseph Caldera, FEAF bomber commander, did fly an assessment mission in April; he found many practical problems with the draft proposals. Assessments of feasibility differ; another report says that Caldera thought a day mission was feasible and could be launched in 72 hours. 
One technical unknown involves the weather over Dien Bien Phu. In principle, B-29 bombers could bomb fairly accurately, especially in daylight, above the range of Vietnamese antiaircraft guns. That was also true in principle over Japan in the Second World War, but unexpected high-altitude winds made that impossible. Still using unguided bombs, U.S. B-52 bombers were able to carry out accurate high-altitude bombing over the North during the 1972 Operation LINEBACKER II.