CHARLESTON, W.Va. (AP) _ Democratic Sen. Jay Rockefeller closed the door on Wednesday to a 1992 bid for the White House, saying the campaign would have eaten up all his time and ''every single ounce of energy,'' leaving no chance to plan a national administration.

Without time to prepare, he said, he was not ready to be president.

Rockefeller had publicly flirted since May with running for the Democratic nomination to unseat George Bush. He denied that his decision not to do so had anything to do with polls showing the public wants the president to stay president.

''George Bush can be beaten. That's why you're not only going to see the candidate who's in there now, but you're going to see three or four or maybe five more candidates in there,'' Rockefeller said.

Former Sen. Paul Tsongas of Massachusetts, the only Democrat in the race so far, said he believed ''it would be difficult to start a campaign at this late date.''

As for himself, said Rockefeller, ''The fundamental question ought to be - and has to be in my own mind - governance. Are you ready at this particular point to fully say that you are ready to govern America with full thought beforehand, and I cannot say that at this point.''

''What has become clear to me,'' if he were to run now, said Rockefeller, ''is that from the moment I announced my candidacy I would be obligated to devote every single waking hour, every single ounce of energy to the process and to the mechanics of a mammoth national campaign.''

''Sacrificed during that campaign would be the critical time necessary to focus on governing, on governing our country, to plan a Rockefeller administration - something that in fact I have only had the last three months to do,'' he said.

''Three months, frankly, has just not been enough time for me to be fully ready for a Rockefeller presidency that fully meets my high standards,'' he said.

Rockefeller's decision comes two weeks after House Majority Leader Richard Gephardt of Missouri announced he would not run in 1992.

But Iowa Sen. Tom Harkin and Arkansas Gov. Bill Clinton are considered likely to join Tsongas in the race next month, and Sen. Albert Gore Jr. of Tennessee and Virginia Gov. L. Douglas Wilder also are considering running.

Rockefeller said all would merit his support, saying he spoke with Gore on Tuesday night and planned to phone Harkin after his announcement.

''One of the qualities which they do bring, which I don't, is that each of them has had a much longer period of time, certainly longer than three months, to consider the whole question and scope and sense of the presidency itself,'' he said.

Clinton, like Tsongas, praised Rockefeller and said he was ''sort of sorry'' to hear he was not running. Clinton also said the development ''certainly won't be a discouraging factor'' in his own decision whether or not to run.

After campaign-like trips through 22 states, including New Hampshire, Texas and Iowa, Rockefeller huddled with family members last weekend at his Pocahontas County home to make his decision.

Rockefeller said his he didn't dabble with a 1992 campaign to enhance his prospects for a presidential bid in 1996. ''This isn't a practice run,'' he said, but ''I obviously don't preclude the presidency later on.''

Pennsylvania State Democratic Chairman Larry Yatch said Rockefeller's bow- out could position him for the No. 2 spot on a Democratic ticket, particularly if New York Gov. Mario Cuomo enters the race.

''My feeling has always been if Mario Cuomo were successful at gaining the nomination, that Jay would be an excellent strong second part to that ticket,'' Yatch said.

Rockefeller said he wasn't interested in becoming vice president. But ''I'm not going to be standing on the sidelines. I'm going to be fully participatory in this election,'' he said.

Rockefeller, 54, is a great-grandson of oil baron John D. Rockefeller and nephew of the late Vice President and New York Gov. Nelson A. Rockefeller.

He was raised in New York but went to West Virginia in 1964 as a poverty program volunteer. Within two years, Rockefeller had abandoned his family's Republican politics and won election to the state House of Delegates as a Democrat. He was governor from 1977 to 1984 and was first elected to the Senate in 1984.