NEW YORK (AP) _ Americans in two public opinion polls strongly defended the United States for shooting down an Iranian passenger plane early this month, although both surveys were conducted before many details were known.

In an ABC News-Washington Post poll conducted July 5, two days after the incident, 71 percent of respondents said the U.S. action was justified and 74 percent said Iran overall was more to blame for the incident.

In a USA Today-Cable News Network poll conducted the same day, 75 percent said the shooting was justified based on what was known at the time and 61 percent said Iran was more responsible than the United States for the incident.

Immediate one-day polls such as these often measure visceral reactions rather than thoughtful opinion. Their sample sizes are about half that of most national surveys.

The United States initially claimed that the Iran Air jet with 290 people aboard was outside a commercial air lane when a Navy warship shot it down. The United States later withdrew that claim, after the polls had been conducted.

The Navy has said its warship, the USS Vincennes, mistook the jet for an Iranian F-14 fighter, and that it fired after the jet failed to respond to repeated radio warnings. It has said the jet took off an hour later and appeared to be descending in what was seen as a hostile flight pattern.

The British intelligence agency reportedly has supported Iran's claim that the jet took off on time and was climbing, not descending, when it was shot down. That report also came after the polls were conducted.

In other findings in the ABC-Post poll, 72 percent said the downing was ''an understandable accident'' rather than ''a stupid mistake,'' 80 percent said the captain of the Vincennes acted properly and 61 percent opposed U.S. payments to families of the victims. In the USA Today-CNN poll, 48 percent opposed financial compensation to the families.

The ABC-Post poll was conducted by telephone among 524 adults, the USA Today-CNN poll among 646. Both had error margins of about 4 points.