A majority of Americans interviewed in a Washington Post-ABC News poll say they disapprove of the Reagan administration's plan to develop a space-based missile defense in light of the criticisms lodged against it.

Support for the administration's Strategic Defense Initiative (SDI), which some call "Star Wars," would drop even more if its development should require the United States to violate or abandon the Antiballistic Missile Treaty with the Soviet Union, the survey found.

The nationwide poll of 1,506 people, conducted July 25 to July 29, showed that 53 percent disap- proved of the program, 41 percent approved, and 5 percent said they were uncertain or had no opinion.

The response came in answer to a question that pitted the basic argument for "Star Wars" -- protection from nuclear attack -- against criticism that the system would be expensive, might not work and could escalate the arms race.

Those who said they approved were then asked whether they still would favor it if it meant violation or abandonment of the ABM treaty. Sixty-three percent of this group said they would still support it, 32 percent said they would not, and 5 percent didn't know or had no opinion.

Put another way, the survey found that 26 percent of all those polled said they supported development of a space-based missile defense even if it should conflict with the treaty.

The 1972 ABM treaty prohibits both the United States and the Soviet Union from developing, testing or deploying ABM systems or components "which are sea-based, air-based, space-based, or mobile land-based."

The SDI debate could turn into a potent political issue, the poll suggests.

Support for it was strongest among people who voted for Pres- ident Reagan in 1984 (59 percent), those who call themselves Republicans (59 percent) and those who consider themselves conservatives (56 percent).

Opposition was strongest among those who voted for Walter F. Mondale (73 percent), those who disapprove of the Reagan presidency (70 percent) and those who call themselves Democrats (69 percent).

There is also evidence of a striking gender gap on the initial question. Men approved development of space-based weaponry to knock down Soviet missiles by 54 percent to 43 percent. But only 30 percent of the women approved, while 63 percent disapproved.

The findings contrast sharply with other, differently worded polls on the subject, such as a February 1985 survey by Arthur J. Finkelstein of New York and a May 1985 poll conducted by Sindlinger & Co. for the Heritage Foundation's Policy Review.

The Finkelstein poll said 90 percent responded yes when asked, "Do you want the United States to defend Americans against Soviet missiles?" It also said 83 percent answered no when asked, "Did you know that the United States has a treaty with the Soviet Union not to protect Americans from a Soviet missile attack?"

The Sindlinger poll in May said current U.S. policy is "to deter a Soviet nuclear attack by threatening massive retaliation, while at the same time leaving the United States defenseless against a Soviet nuclear attack." It found that 74.4 percent felt that this strategy "needs to be changed."

The poll also said that 69.1 percent favored development and eventual deployment of a "Star Wars" defense system "even if it meant that the U.S. would have to renegotiate or withdraw from our existing arms control agreements with the Soviet Union."

The questions in the Post/ABC News poll and the results:

Q. Have you read or heard about plans by the Reagan administration to develop weapons in outer space that could destroy nuclear missiles fired at the United States by the Soviet Union or other countries? Reagan calls the research on these weapons SDI, for Strategic Defense Initiative, and some people refer to it as "Star Wars."

Yes, have read or heard 84 percent.

No, have not read or heard16 percent.

Don't know or no opinion 1 percent.

Q. Supporters say such weapons could guarantee protection of the United States from nuclear attack and are worth whatever they cost. Opponents say such weapons will not work, will increase the arms race, and that the research will cost many billions of dollars. How about you: would you say you approve or disapprove of plans to develop such space-based weapons?

Approve 41 percnt.

Disapprove 53 percent.

Don't know or no opinion 5 percent.

Q. (For those who approved) Currently the U.S. and the Soviet Union have an anti-ballistic missile treaty that prohibits both nations from developing certain weapons. Suppose the U.S. had to violate or abandon that treaty in order to develop the space-based weapons. Would you still favor development of those space-based weapons, or not?

Yes, would still favor/63 percent.

No, would not still favor/32 percent.

Don't know or no opinion/5 percent.