The United States is also resorting to a military threat. Tian noted that the carrier USS John C. Stennis has arrived in the Persian Gulf region and two U.S. carriers are currently deployed south of Iran. During his recent trip to Australia, U.S. Vice President Dick Cheney refused to rule out the possibility of taking military action against Iran, saying that "all options are still on the table" over Tehran's nuclear program.

It deals blows to Iran's activities in Iraq, too, Tian said. The U.S. military has announced that there is reliable evidence showing Iran provides weapons and training to anti-U.S. forces in Iraq. As it brings shame on Iran, it continues to shatter its "Shiite network" in Iraq and its influence there, the expert noted.

Moreover, the United States is pursuing financial sanctions on Iran by encouraging some banks in the West to reduce their business or stop doing business with Iran, he added.

Finally, it renders support to Tehran's opponents, Tian noted. While secretly supporting armed national separatists to disrupt Iran's social order and exert pressure on the government, it seeks to establish a "regional anti-Iranian alliance."

Meng said the United States has three aims in Iran. The first and foremost is to topple the Iranian Government and change Iran's social system. The second one is to terminate all of Iran's nuclear development, civilian and military programs alike. Its lowest aim, however, is to prevent Iran from manufacturing nuclear weapons.

He identified several conditions that may affect Washington's decision on whether to take military action against Iran. The decision depends on whether there is sufficient evidence to show that Iran has started to develop nuclear weapons as it pursues its nuclear program. It also hinges on the extent to which Iran supports anti-U.S. forces in Iraq. In short, he argued that the possibility of a U.S. military attack on Iran is mainly determined by the substantial compromise Iran makes on the nuclear issue.

He continued that Iran and the United States are wrangling with each other using a two-pronged strategy. At present, he observed, the main tactic of the United States is to use diplomatic pressure and a military deployment, noting that it would be best if the countries could reach a diplomatic settlement.

Tian echoed this view. He noted that both countries have other alternatives to resolve the issue and the situation today is not "either war or peace." Also, as the United States faces daunting challenges in Iraq and Afghanistan, it cannot afford to devote too much attention to Iran. In this context, it may opt for diplomatic pressure or other deterrents to retard the progress of Iran's nuclear program, the expert said.

Despite this, Tian is cautious about the underlying risks. He noted that as the two countries practice highly antagonistic policies, they might allow the situation to deteriorate to the brink of war. Washington's tough approach at the beginning of this year shows that the United States is losing patience with Iran. Iran's refusal to honor the UN resolution has lessened the international resistance toward possible U.S. military attacks. As it completes its military deployment, the United States is set to adopt a more hostile policy toward Iran, he said.