The Arak IR-40 heavy water reactor in Iran. Photo: Nanking2012/Wikimedia Commons.

Iran could begin producing weapons-grade plutonium by next summer, using nuclear technology more easily exposed to foreign attacks and thus increasing the likelihood of an Israeli strike on Iranian nuclear facilities, US and European officials told The Wall Street Journal Monday.

According to The WSJ report, the West believes Iran could use the development of a heavy water nuclear reactor to produce plutonium for a bomb. The heavy-water reactor is an easier target to hit than the underground facilities that currently house Iran’s uranium-enrichment facilities.

Iran has notified the International Atomic Energy Agency, the U.N.’s nuclear watchdog, that it plans to make the reactor—located in the northwestern city of Arak—operational by the second half of 2014 and could begin testing it later this year.

Spent fuel from the reactor contains plutonium—which can serve as the raw material for an explosive device. India and Pakistan have built plutonium-based bombs, as has North Korea.

Once completed, US and European officials believe the facility will be capable of producing enough plutonium for two nuclear bombs a year.

Iran denies it is seeking nuclear weapons and claims the Arak facility will produce isotopes used in medical treatments, U.N. officials have said.

“There’s no question that the reactor and its heavy water are more vulnerable targets than the enrichment plants,” Gary Samore, who served as President Barack Obama’s top adviser on nuclear issues during his first term, told The WSJ. “This could be another factor in [Benjamin] Netanyahu’s calculations in deciding how long to wait before launching military operations.”

Any Israeli strike on the reactor complex, said current and former U.S. officials, would likely have to take place before Tehran introduces nuclear materials into the facility, because of the potential for a vast environmental disaster that a strike could cause.

Netanyahu has repeatedly pledged to target Iran’s nuclear facilities if international diplomatic efforts fail. Appearing on CBS’s “Face the Nation” in July he warned Iran not to move forward with the commissioning of the Arak reactor.

“They’re pursuing an alternate route of plutonium…to build a nuclear bomb,” the Israeli leader said on July 14. “They haven’t yet reached it, but they’re getting closer to it. And they have to be stopped.”