A US attack on Iran’s nuclear facilities would be a drawn-out process that could only set Tehran’s program back by a few years, a former top US military official said Wednesday.

Admiral William Fallon’s remarks to a research institute went a step further than similar remarks by other US officials, including Joint Chiefs of Staff head Martin Dempsey, who had previously warned that a solo Israeli strike on Iran’s nuclear program would have limited success.

“If the US were to put a full-fledged strike campaign in there, that would probably take several weeks, it could put this program back for several years,” Fallon told the American Security Project, AFP reported.

Fallon, a former Central Command head, last year signed a report calling on the US government to do everything to avoid engaging Iran militarily. Other members of the “realist” political camp, including defense secretary nominee Chuck Hagel, also signed the report.

Israel sees Iran’s nuclear program, widely believed to be for militarization purposes, an an existential threat, and has been working to muster US backing for a military strike should diplomacy and sanctions fail.

Fallon said a strike on Iran would be much more complex than solo Israeli strikes on nuclear facilities in Iraq and, reportedly, Syria, in 1981 and 2007, respectively.

“The bottom line is, it’s not going to be a one-time shot. It’s not going to be like ’81 or even 2007,” Fallon said.

He added that he hoped for a diplomatic solution to the issue.

Talks aimed at curbing Iran’s enrichment activities, which Tehran says are for peaceful purposes, are set to pick up between the Islamic Republic and the six world powers known as the P5+1 later this month.

The six nations —the United States, Russia, China, Britain, France and Germany — hope the talks will result in an agreement under which Iran would stop enriching uranium to a higher level that could be turned relatively quickly into the fissile core of nuclear arms.

Meanwhile, officials from the International Atomic Energy Agency, a UN-linked nuclear watchdog, are currently holding parallel talks in Iran over a bid to gain access to nuclear sites for inspection.

So far, neither track has produced results.

Before departing Tuesday for Iran, UN team leader Herman Nackaerts said the IAEA hoped to “finalize the structured approach” that would outline what the agency can and cannot do in its investigation.

The Associated Press contributed to this report.