Iran says it has successfully test-fired the longest-range missiles in its arsenal, weapons that are capable of carrying a warhead and striking Israel and parts of Europe.

Iranian state television says the Revolutionary Guard's third round of missile tests in two days successfully tested upgraded versions of the medium-range Shahab-3 and Sajjil missiles. Both can carry warheads and hit targets up to 2,000 kilometres away. Such a range would put Israel and U.S. bases in the region within striking distance.

The missile tests come as tensions escalate in Iran's nuclear dispute with the West, following last week's disclosure by Tehran that it is building a second uranium enrichment plant.

The facility was revealed in the mountains near the holy city of Qom and is believed to be inside a heavily guarded, underground facility belonging to the Revolutionary Guard.

Iran's Foreign Ministry said there was no link between the missile maneuvers and the country's nuclear activities, insisting the tests are part of routine, long-planned military exercises and are meant to show that Tehran is prepared to crush any outside military threat.

"This is a military drill which is deterrent in nature," spokesman Hassan Qashqavi told a news conference broadcast by English-language Press TV. "There is no connection whatsoever with the nuclear program."

But the testing adds a sense of urgency to a key meeting on Thursday in Geneva between Iran and six major powers that are trying to stop Iran's suspected nuclear weapons program, including the United States, China and Russia.

Jim Walsh of the Security Studies program at the Massachusetts Institute of Technology said the timing of the testing is not a coincidence.

"Often when a country is about to go into negotiations with the international community, which is what's happening on Oct. 1, countries have a tendency to make a show of strength," he explained to CTV's Canada AM on Monday from Boston.

"That sends a signal to the domestic population that says, 'Hey, just because we're going into negotiations doesn't mean we're weak.' And it also sends a message to those folks that'll be across the table saying, 'Take us seriously, we're strong'," Walsh said.

Ellen Laipson, the president of Stimson, a nonprofit public policy institute that focuses on the security challenges facing the U. S., says she expects this week's meetings in Geneva will allow Iran to insist that its nuclear ambitions are purely benign.

"I expect the Iranians' opening position will be very high-level conceptual posturing; you know: how the West is at fault for instability in the world, that Iran has an alternative idea and Iran only wants peace," she told Canada AM from Chevy Chase, MD.

"'Iran's argument on its nuclear activities is that it is for peaceful purposes, that eventually they will no longer be able to rely on their petroleum reserves. So they've made the argument that all countries are entitled to develop peaceful nuclear energy so long as they also comply with the other measures that assure the international community that they're not pursuing a weapons program."

Laipson says that means Iran will be under intense pressure to fulfill the promise it made over the weekend to allow United Nations nuclear inspectors to examine the site.

U.S. Secretary of State Hillary Clinton has said she doesn't believe Iran can convince the U.S. and other world powers at the upcoming meeting that its nuclear program is for peaceful purposes. That puts Tehran on a course for tougher economic sanctions beyond the current "leaky sanctions," she said.

U.S. President Barack Obama also warned that Iran would face "sanctions that bite," but also stressed the need for diplomacy.

MIT's Walsh says he's all for tightening sanctions, but he's not convinced that the sanctions, which date back 30 years, have worked.

"I think sanctions are part of this puzzle but it's a mistake to think that sanctions alone are going to force Iran to wave a white flag and give up a program that it has so publicly committed to," he said.

"At the end of the day, President Obama is correct: it's negotiation that will begin to solve this problem."