US Defense Secretary Robert Gates said on Monday the United States has no evidence that Iran's government is behind a flow of weapons from Iran to Taliban insurgents in Afghanistan.
On his second visit to Afghanistan since taking over the Pentagon in December, Gates met Afghan President Hamid Karzai, who also said there was no evidence that Iran was supplying the Taliban.
"There have been indications over the past few months (that) weapons are coming in from Iran," Gates told a news conference with Karzai at the national palace.
We do not have any information about whether the government of Iran is supporting this, is behind it, or whether it is smuggling, or exactly what is behind it."
"But there clearly is evidence that some weapons are coming into Afghanistan destined for the Taliban, but perhaps also for criminal elements involved in the drug trafficking coming from Iran," he said.
US officials accuse Iran of meddling. The top US general, Joint Chiefs of Staff Chairman Peter Pace, said on Sunday that Iranian-made weapons had been found inside Afghanistan.
Gates' one-day visit is aimed at assessing coordination within the US-led coalition to ensure Afghanistan does not spiral into the kind of violence seen in Iraq.
Afghanistan is the world's largest producer of opium and supplies about 90 per cent of the world's heroin. Authorities say heroin profits help fund the Taliban, waging an insurgency since they were ousted from government by a US-led invasion in 2001
Taliban violence has picked up in recent weeks following a traditional winter lull in fighting, despite the presence of nearly 50,000 NATO and US-led coalition troops in Afghanistan.
Taliban suicide bombers strike several times a week and have recently moved into relatively peaceful northern areas of the country. The Taliban has said it has trained hundreds of suicide bombers.
Karzai said Afghanistan's relationship with Iran had never been better.
"We don't have any such evidence so far of the involvement of the Iranian government in supplying the Taliban," he said
In contrast, Afghan National Army chief Bismillah Khan said earlier in the day that Afghanistan was not getting enough cooperation from neighboring Pakistan.
"We have a relationship, of course, under the coordination of the United States," Khan said as he and Gates toured a commando training centre on the outskirts of Kabul. "The cooperation that we need, unfortunately, we don't get."
Khan said the two countries needed a better exchange of information and more joint training exercises.
Relations between the uneasy neighbors, both US allies in its war on terrorism, have deteriorated in recent months. The worst violence in years erupted three weeks ago in a disputed border area in Afghanistan's southern Paktia province.
Afghanistan said Pakistan invaded its soil and killed 13 Afghans. Pakistan said Afghan troops started unprovoked firing on border posts.