Iran's Foreign Ministry Spokesman Ramin Mehmanparast has described accusations by the US secretary of defense against Tehran as a "big lie," Press TV reported.
The American new defense chief Leon Panetta, who is on an official but surprise visit to Iraq, claimed on Monday that the US is "very concerned about Iran and the weapons they're providing to extremists in Iraq."
The Iranian official mocked the unsubstantiated US claim by saying, "It seems that the Americans do not have a favorable position in the region, especially in Iraq and Afghanistan, so they are making every effort to continue their presence in these countries at any cost."
Mehmanparast added that Washington was making desperate efforts to find a way extend its stay in the region "since the Americans are facing a widespread wave of opposition by the Iraqi people, government and [political] parties, and they must leave Iraq by the end of 2011 and Afghanistan by the end of 2014."
On Monday, Iran's Foreign Minister Ali Akbar Salehi also rejected Panetta's allegations.
"The international community and world public opinion are well aware that Iran as a responsible country has always behaved in a way [that has seen] its duties carried out well," Salehi said.
The United States and its allies sent their troops to Iraq in 2003, citing concerns over alleged weapons of mass destruction (WMD) wielded by the executed Iraqi dictator Saddam Hussein's Ba'athist government.
No such weapons were ever found in Iraq.
In August 2010, the United States declared an end to its combat mandate in Iraq but left 50,000 of American troops in the country for what it called "advising and training" purposes.
The US forces, however, are expected to fully withdraw from Iraqi soil by the end of 2011.