The White House says it is prepared to work with the new President of Iran if Iran will "engage seriously" with international concerns like its nuclear programme.
But after President Hassan Rouhani took the oath of office before parliament in Tehran, he warned the West that it must "speak the language of respect."
ITV News Diplomatic Correspondent John Ray reports from Washington.
President Rouhani has called for talks based on mutual respect and urged the West to lift sanctions that have crippled Iran's economy - in return he will have to offer concessions on Iran's nuclear programme.
The 64-year-old arrives in power at the start of 12 months which are seen as make or break for the international effort to prevent Iran from acquiring nuclear weapons.
The resounding victory of the politically relatively moderate leader in June's election raised hopes of negotiating an end to the nuclear dispute and an easing of the sanctions that have hit the OPEC country's oil exports.
Read more: Iran's president sworn in
The White House says that Rouhani would find "a willing partner" in the US if his government decided "to engage substantively and seriously" in honouring its international obligations.