US Secretary of State Hillary Clinton welcomed Australian and European sanctions against Iran, saying she hoped they would influence Iran to take a "more constructive course".
"These measures are part of the international community's vigorous effort to build upon UN Security Council Resolution 1929 and address Iran's noncompliance with its international obligations," Clinton said in a statement.
"They send a clear message to Iran's leaders: Uphold your international responsibilities or face growing international isolation and consequences."
Clinton reiterated that Washington and its allies "are committed to engaging Iran in pursuit of a diplomatic resolution to the international community's concerns regarding Iran's nuclear programme and other issues.
"We hope that Resolution 1929 and these additional measures will affect the strategic calculus of Iran's leaders and influence them to take a more constructive course."
The new European Union sanctions, imposed on Thursday, include a ban on new investment, technical assistance and technology transfers to Iran's huge gas and oil industry, particularly as regards refining and liquefied natural gas.
The new EU measures also target the Islamic Republic's transportation, banking and insurance sectors and slap new visa bans and asset freezes on the Islamic Revolutionary Guard Corps (IRGC).
Australia's sanctions apply to Bank Mellat, a major financier of Iranian missile and nuclear programmes, as well as a major Iranian shipping line and a "key leader" of the Revolutionary Guard, General Rostam Qasemi.
New US sanctions imposed on Wednesday target insurance companies, oil firms and shipping lines linked to Iran's atomic or missile programmes as well as the IRGC and Iran's Defence Minister Ahmad Vahidi.
The United States has long offered Iran trade and other incentives in exchange for halting its uranium enrichment programme, which Western powers fear masks a drive to build a nuclear bomb.
Iran claims its aims are peaceful.