RCA Corp. and C.I.T. Financial Corp. today ended their merger discussions, barely a week after RCA, which owns the National Broadcasting Co., approached the finance company.

Wall Street analysts said the acquisition would have been worth more than $1 billion, assuming RCA would pay between $60 and $67 a share -- but neither company mentioned a negotiating price in their terse statements to the press last week and this week.

The price of the C.I.T. stock plumeted $12.125 a share today closing at $41.375 C.I.T. was the second most active stock on the New York Stock Excahnge as 741,000 shares changed hands.

RCA closed up one-eight to $24.75 a share.

Neither company would comment on the end of the discussions.

RCA Chairman Edgar H. Griffiths told stockholders last spring that the communications and electronics conglomerate is interested in making acquisitions in the financial services field.

Analysts speculated today that RCA might have been put off by the generally adverse reactions investors gave RCA after it was announced last week. that the two companies were talking merger -- with RCA the acquiring company.

"While C.I.T. stock rallied, RCA just sat there," one analyst noted.

"It would be that someone else was coming down the pike with an interest in C.I.T. and RCA didn't want to get involved in a bidding war," another analyst speculated.

But most analysis is just speculation. Officials at neither company would say anything about the course of the negotiations or what caused the sudden breakoff in the talks.

Only last Tuesday, C.I.T. Chairman Walter S. Holmes Jr. -- who worked with Griffiths for 14 years at RCA until he left in 1962 -- announced that the finance company had been approached "by a major U.S. corporation" that he would not identify.

C.I.T. has stated several times that it would be willing to merge on friendly terms if the right offer came along.