Obama is beset by questions about President Hamid Karzai's popularity, honesty and management of the war against Taliban, while Kennedy dealt in 1963 with President Ngo Dinh Diem and his inability to turn the tide against Viet Cong insurgents.

At issue in both conflicts was a rising number of U.S. casualties in defending unpopular governments.

Forty-six years ago this week, Vietnamese generals, confident they had the support of their U.S. allies, overthrew Diem's government in Saigon. But Kennedy, conflicted by a State Department green light to the generals in their coup, questioned the move.

"I don't see any reason to go ahead unless we think we have a good chance of success," Kennedy told his advisers a few days after the department's cable was sent in August 1963 to Saigon.

Audio tapes and transcripts of four days of White House meetings released this week by the JFK Presidental Library in Boston reflect uncertainty over what steps to take to try to bolster Saigon's government, riddled with corruption and out of touch with its citizens.

Diem, the South Vietnamese president, and his brother, Ngo Dinh Nhu, were killed in the coup. The assassinations were not discussed in the White House meetings, Kennedy Library Archivist Maura Porter said Tuesday.

While the released tapes showed his reservations, the tapes did not show whether Kennedy tried to stop the coup.

Cable 243 was transmitted by the State Department without the direct approval of key presidential advisers. It said "if Diem remains obdurate and refuses" to remove his brother, who was his security adviser, "then we must face the possibility that Diem himself cannot be preserved."

But Kennedy, according to a transcript, said: "I don't think we ought to just do it (the coup) because we feel we have to now do it. I think we want to make it our best judgment because I don't think we have to do it."

During the discussions, State Department officials said they felt it was too late to step back from supporting a coup. Disagreeing, Kennedy said: "I don't think we ought to take the view here that this has gone beyond our control because I think that would be the worst reason to do it."

The State Department cable called for President Diem to remove his brother from a position of power and threatened U.S. support for a military coup in South Vietnam if he refused, according to the tapes.

With the cable, the United States "started down a road that we really never recovered from," Robert F. Kennedy is quoted as telling historian Arthur Schlesinger.

The battlefield situation gradually worsened for South Vietnam and the United States, and the conflict drew to a close under President Richard M. Nixon.

All U.S. ground troops were gone by March 1973, and the United States evacuated Saigon in April 1975. Normal relations were established with Hanoi in 1995.

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On the Net:

Cable 243 on possible removal of Diem: http://tinyurl.com/ylhzayg

Excerpts from White House tapes: http://tinyurl.com/yfcbq8b

Audio of Kennedy on coup: http://tinyurl.com/ylk9zvg

Audio of Kennedy and top Vietnam advisers: http://tinyurl.com/ygry5v3

Audio of oral history with Frederick Nolting, former ambassador to Vietnam: http://tinyurl.com/yhxyyfh

Archival documents slideshow: http://tinyurl.com/yknaopd