PARIS — A senior U.S. diplomat accused Iran yesterday of transferring weapons to Taliban insurgents in Afghanistan — the most direct comments yet on the issue by a ranking American official.

Undersecretary of State Nicholas Burns, speaking to reporters in Paris, said Iran was funding insurrections across the Middle East — and “Iran is now even transferring arms to the Taliban in Afghanistan.”

“It’s a country that’s trying to flex its muscles, but in a way that’s injurious to the interests of just about everybody else in the world,” he said. “I think it’s a major miscalculation.”

In Afghanistan last week, Defense Secretary Gates said Iranian weapons were falling into the hands of Taliban fighters, but stopped short of blaming the government itself.

Iran’s possible role in aiding insurgents in Iraq has long been hotly debated, and last month, some Western and Persian Gulf governments charged that the Islamic government in Tehran is also secretly bolstering Taliban fighters.

In an interview with the Associated Press on Monday, Army General Dan McNeill said Taliban fighters are showing signs of better training, using combat techniques comparable to “an advanced Western military” in ambushes of U.S. Special Forces soldiers.

“In Afghanistan it is clear that the Taliban is receiving support, including arms from … elements of the Iranian regime,” Britain’s Prime Minister Blair wrote in the May 31 edition of the Economist.

Iran, which is also in a dispute with the West over its nuclear program, denies the Taliban accusation, calling it part of a broad anti-Iranian campaign. Tehran says it makes no sense that a Shiite-led government like itself would help the fundamentalist Sunni movement of the Taliban.

Mr. Burns also criticized Iran’s perceived intransigence over its nuclear program, which many Western powers fear masks a plan to build weapons — though Iran says its intentions are to generate energy.

Mr. Burns insisted new U.N. Security Council measures were needed “so that the Iranians don’t have business as usual.”

“We will have to move forward at the Security Council for a third … resolution in a matter of weeks,” he said.

The council imposed sanctions on Iran on December 23 for refusing to suspend uranium enrichment despite U.N. demands, and modestly increased the sanctions March 24 when Tehran stepped up its enrichment program.

“We believe that beyond [the third resolution], Europe and the Asian countries and Middle Eastern countries will have to adopt even harsher sanction measures outside the Security Council,” Mr. Burns added.