Accused kidnaper Glenn I. Wright, in a surprise move, took the witness stand yesterday and acknowledged planning and executing the abduction of a wealthy businessman's wife last July for a $1 million ransom, saying his only other option was suicide.

Wright's testimony, on the seventh day of his trial in U.S. District Court here, came despite reminders from his lawyer, William Garber, and District Judge Oliver Gasch that he was not required to testify.

Wright testified that he began to develop the kidnap plan in his Houston condominium on the weekend of July 7-8, after two business ventures had fallen through. A third project appeared about to fail and he was in serious financial difficulty.

Wright also was under mounting emotional pressure, he said, from the fatal shooting of his homosexual lover in Wright's home in early 1983 and the slow death of his mother from Alzheimer's disease in August of that year.

Wright also revealed that, three days before the kidnaping of Edith Rosenkranz from the Washington Sheraton Hotel, he flew to New York, rented a safe deposit box for the ransom money, then returned to Washington to resume stalking Rosenkranz.

Wright, 42, and a codefendant, Dennis Moss, 26, both of Houston, were arrested on the evening of July 21 after releasing Rosenkranz on the Mall. Both face a maximum sentence of life imprisonment if convicted.

Wright, whose defense is based on a claim that he was insane at the time of the offense, testified coherently yesterday, halting often to dab his eyes with a tissue and occasionally weeping.

Wright said he was driving from San Antonio, Tex., to Houston one evening last June after learning that a third and final real estate venture was likely to fail when "I thought in the back of my mind that I was not going to survive this."

"I was very depressed and feeling sorry for myself and I thought, 'Glenn, you are going to have to die,' " he testified.

Shortly afterward, however, Wright said he came across a bridge bulletin in his condominium that mentioned an upcoming summer bridge tournament in Washington.

Wright, a life master bridge player, said he knew that the Rosenkranzes, who are well-known in competitive bridge circles, were likely to attend the tournament. "Something clicked," Wright said, "and I began to think maybe there's another way out."

Wright said he began to plan a kidnaping in which nobody would be hurt. "That was paramount," he testified.

Wright said he had bought a .38-caliber revolver after the death of his lover and roommate, Tony Ivey, 23, an unsolved homicide. As he planned the kidnaping, he testified, he put the revolver to his head several times, but later resolved to use sleeping pills if he killed himself.

The government produced the gun in court last week as the weapon used in the Rosenkranz abduction.

Wright testified that he met Moss in a Houston bar and recruited him to kidnap Rosenkranz.

On July 16, three days before the abduction, Wright said, he took the shuttle to New York and rented a safe deposit box at a Chemical Bank branch in lower Manhattan.

Before returning to Washington, he testified, he walked along 42nd Street, looking at the "gay, trashy porno establishments on that street and it was almost as if I was already holding the money [the $1 million ransom]" in his briefcase.

"I felt I was controlling events for the first time in a long time, strange as that may seem. I knew that events in my life were out of control . . . . Walking back through that trash, it was as if I were controlling things."

Moss' lawyer and federal prosecutors are expected to begin cross-examination of Wright when the trial resumes today.