Iran's Defence Minister Ali Shamkhani has warned the US it will use force if it enters its airspace for attacks on Afghanistan.
But Iranian officials have left open the possibility of joining a UN-led campaign to control militancy.
Shamkhani also acknowledges for the first time that Iran has been supplying the Afghan opposition Northern Alliance with weapons and said Iran would continue to do so.
"The Northern Alliance has been and is our ally. We have provided weapons to the Northern Alliance and will continue to do so. There will be no change in our support of them," he told reporters.
The United States also has reached out to the Northern Alliance in its campaign against the Taliban who control most of Afghanistan and who shelter bin Laden.
During a visit to Russia, Shamkhani said he would discuss bilateral military issues including signing arms deals, developments in the Caspian Sea as well as possible U.S. military strikes against Afghanistan.
The US could launch attacks from Pakistan or from warships in the Arabian Sea without violating Iranian airspace.