Iran plans to develop a missile to outdistance its predecessor, which is already capable of striking Israel or U.S. troops in Saudi Arabia, the Iranian defense minister said Saturday.

Iran displayed its medium-range Shahab-3 missile during a military parade Friday. The missile, which Iran tested in July, has a range of 800 miles."Certainly we will work on the development of the Shahab-4 and 5, but this does not mean we will start tomorrow," said Defense Minister Ali Shamkhani.

In July, Assistant U.S. Secretary of State Martin Indyk said Iran was working on the Shahab-4, which he called a greater threat than the Shahab-3. He said the Shahab-4 could be deployed in two to five years and pledged that the United States would redouble its efforts to curb the transfer of technology Iran needs to develop it.

In Israel, Labor Party lawmaker Ephraim Sneh called for a pre-emptory strike against Iran, Army radio reported Saturday.

It quoted him as saying that Israel cannot sit by while the world is being "slack" in dealing with Iran.

Iran is believed to have received substantial missile technology from Russia and some from China and North Korea. The Shahab-3 is believed to be based on North Korea's No Dong ballistic missile.

Shamkhani, a Navy rear admiral, denied at a news conference that Iran had received help in developing the missiles.

Shamkhani said Iran would strike back at Israel if the Jewish state attacked its nuclear plant in the southern town of Bushehr. Israel has warned it has the capability to launch a pre-emptive attack against the nuclear facility.

"We'll certainly respond firmly to any Israeli attack or aggression in a manner more severe than one can imagine, and we have the capability. The most obvious, but only the minimum, is the Shahab-3," Shamkhani said.

Shamkhani would not say how many missiles Iran possessed, but indicated that Iran could produce as many as it needed.

Iran says the Shahab-3 can carry a one-ton warhead at a cruising altitude of 155 miles above sea level.

U.S. and Israeli officials have expressed concern about the missile because it can hit Israel and U.S. troops stationed in Saudi Arabia. Iranian officials have said the missile is only for defense and that they are free to strengthen their armed forces.

Iran had virtually no arms industry under the U.S.-supported shah because Washington supplied nearly all of Iran's defense needs. The shah was ousted during the 1979 Islamic revolution.

The Iranians launched an ambitious arms development program during the 1980-88 war with Iraq to compensate for weapons shortages caused by a U.S. embargo.