Iran's President Mahmoud Ahmadinejad spent much of his U.N. speech yesterday complaining of "bullying" by the West. Funny - in addition to its well-known bloody works in Iraq and Lebanon, Tehran's meddling in Afghanistan is a major, and rising, menace.

Tehran is aiding the Taliban and other anti-government insurgents with weapons and training. It's also pouring spies over the border - and forcing Afghan refugees to return home. Up 'til now, Pakistan was Afghanistan's biggest problem - the host for Taliban safe havens in the border tribal areas. But now Tehran is becoming another major source of trouble.

U.S. Deputy Secretary of State John Negroponte points to weapons shipments to Iran that are finding their way into the mitts of Taliban and other insurgents.

For instance, a 10-ton weapons cache recently was found in Herat, along the Afghan-Iranian border. It included artillery shells, land mines, assault rifles, ammunition and rocket-propelled grenades with Chinese, Russian and Iranian markings.

Early this month, NATO forces in Afghanistan pulled off their third - and biggest - interception of a weapons shipment near the Iranian border this year. It included explosively formed projectiles (EFPs) - Tehran's trademark roadside bombs, the kind responsible for so many GI deaths in Iraq.

In the restive southwestern Helmand province, near the Pakistan border, British troops recently seized Chinese HN-5 anti-aircraft missiles, which could be used to down Coalition helicopters, from Taliban fighters. The weapons could have come in via Pakistan, but China is a major arms supplier to Iran - which has been known to pass them along to clients such as Hezbollah.

Some analysts are linking the Iranian arms shipments, along with development of Taliban sanctuaries in Pakistan, to a significant up-tick in fighting this year for the Afghan government forces and their allies.

NATO's top commander in Afghanistan, U.S. Army Gen. Dan McNeil, said this summer that recent improvements in the fighting skills and tactics of the Taliban could be an indication of training by Iranian advisers.

Local officials in border provinces insist that Iranian helicopters have violated Afghanistan's airspace several times this year - and that the central government opponents are being trained in camps in Iran.

Of course, Tehran denies training or supplying arms to anyone in Afghanistan - especially to the Taliban, which was no Iranian ally when it held power - but the evidence against Iran, specifically the Quds Force of the Islamic Revolutionary Guard Corps, is mounting.

Meanwhile, Tehran's spy service, the feared Ministry of Intelligence and Security, is flooding Afghanistan with agents. (Since the two countries have some common ethnic groups, these operatives can blend in.)

Iranian operatives are keeping an eye on Coalition forces, too. Just this week, the top Revolutionary Guard commander crowed that his forces were monitoring U.S. troop movements in Iraq.

Iran is also broadcasting in agitprop, and garnering clout via public and social works. And it's sending cash to sympathetic Afghan Shiite leaders and religious schools - and to warlords with historic ties to Iranian security services.

Tehran is also squeezing Kabul by forcing up to 200,000 (of as many as 2 million) Afghan refugees in Iran to return home - causing a humanitarian nightmare. The move is a clear warning to Afghan President Hamid Karzai: Don't cross us, or the pain we're causing you will only get worse.

In fact, Karzai has been quite reluctant to publicly highlight Iran's interference, saying, "Iran and Afghanistan have never been as friendly as they are today."

That's clearly an exercise in diplomatic relativism. But Karzai has enough enemies already without adding Iran. Indeed, he's been trying to bolster relations with Iran and India as counterweights to testy ties with Pakistan.

Iran has a large population, oil and natural-gas wealth. Historically, it's been a regional power. It naturally has influence over an underdeveloped neighbor like Afghanistan.

But the Iranian regime is seeking hegemony across the region in a bid to become a world power. It's treating Afghanistan as a poker chip in its high-stakes game of preventing the spread of democracy and thwarting U.S. interests.

In short, just like in Iraq, the Iranian regime is trying to advance its own position through the pain and suffering of Afghans, not to mention those protecting them.

Heritage Foundation senior fellow Peter Brookes is a former deputy assistant secretary of defense.