The criticisms came on Wednesday, as Condoleezza Rice, the secretary of state, made her first testimony to Congress in months, exposing her to a grilling from some members of her own party.
Senator Chuck Hagel told Rice, as she appeared before the Senate Foreign Relations Committee: "I don't see, Madame Secretary, how things are getting better. I think things are getting worse. I think they're getting worse in Iraq. I think they're getting worse in Iran."
Rice also had a tense exchange with moderate Republican Senator Lincoln Chafee over the pace of progress towards Israeli-Palestinian peace and the implications of the Hamas victory in Palestinian legislative elections last month.
Rice said: "We will continue to insist that the leaders of Hamas must recognise Israel, disarm, reject terrorism and work for lasting peace."
Though the moderate Chafee and Hagel, a frequent Republican maverick and potential presidential candidate in 2008, are less conservative than many of their Republican colleagues, their criticism underscored a widespread frustration in Congress with the difficult problems the United States is facing across the Middle East.
"I think things are getting worse. I think they're getting worse in Iraq. I think they're getting worse in Iran"
Senator Chuck Hagel
The US and its European allies are confronting Iran over its nuclear programme.
But Tehran has remained defiant and said this week that it is resuming small-scale uranium enrichment, which many countries fear could be an early step towards production of fuel for a nuclear bomb.
Rice said: "They have now crossed a point where they are in open defiance of the international community."
She declined to detail what punishment the United States is pursuing, although she did acknowledge that the United States has analysed the impact of oil sanctions on Iran as part of a broad review of all available tools and has a "menu of options" available.
Democracy in Iran
Rice tried to take the offensive by announcing an administration request for $75 million this year to build democracy in Iran, saying the US must support Iranians who are seeking freedoms under what she called a radical regime.
The money Rice wants for Iran, to be included in an emergency 2006 budget request the White House is expected to send to Congress as early as this week, would be used for radio and satellite television broadcasting and for programmes to help Iranians study abroad.
Rice said: "The United States wishes to reach out to the Iranian people and support their desire to realise their own freedom and to secure their own democratic and human rights. The Iranian people should know that the United States fully supports their aspirations for a freer, better future."
Iranian students will be offered
In April the US said it had set aside $3 million to promote democracy in Iran, saying the initiative does not violate the Algeria non-interference agreement.
At the time, Richard Boucher, the US State Department spokesman, said non-governmental educational and other groups inside Iran, which are willing to work towards achieving democracy in Iran, are eligible to compete for the money.
Muhammad Javad Zarif, Iran's ambassador to the UN, called the plan a clear violation of a US-Iranian agreement which was signed in Algeria in 1981 following the release of 52 US embassy employees held hostage in Tehran for 444 days.
Political analysts and Western diplomats are sceptical of how effective US programmes to promote democracy in Iran can be but note Washington has few other policy options when it is seeking to influence Iranians.
At one point, Rice and Senator Barbara Boxer interrupted each other as they argued about US policy in the Middle East, where the Democrat accused the Bush administration of having a "tin ear" to Arab views.
Boxer, who was one of Rice's most persistent critics during a contentious confirmation process last year, also recalled Rice's warning before the 2003 Iraq invasion that the world could not afford to let the "smoking gun" of Iraq's supposed weapons of mass destruction become a "mushroom cloud".
"The truth is coming out"
Senator Barbara Boxer
"That was a farce and the truth is coming out," Boxer said.
Rice plans a trip to the Middle East next week, including stops in Egypt, Saudi Arabia and the United Arab Emirates, where the issue was sure to arise.