A top US lawmaker vowed Thursday to toughen US sanctions against Iran over its suspect nuclear program and place renewed scrutiny on Russia and China's economic ties with Tehran.

"We can still -- if we get tough, and we put all of the sanctions that we can to bear -- we can still stop Iran from becoming a nuclear superpower," Republican Representative Ileana Ros-Lehtinen, the incoming House Foreign Affairs Committee chair come January, told AFP in an interview.

Ros-Lehtinen said she would look to toughen existing US sanctions on Iran, reining in the White House's ability to waive the application of punitive measures on firms violating US law, and ensure the measure is fully applied.

"I hope to be working with my colleagues in a bipartisan way to toughen the legislation we've already passed, to get rid of some presidential waivers and to do a lot of oversight," she said.

Republicans have complained that President Barack Obama's administration has been slow to investigate whether firms are doing business in Iran in violation of US sanctions laws and sluggish to slap sanctions on scofflaws.

Ros-Lehtinen said she would work with the US Departments of State and Treasury to "try to get them to sanction more companies, look at the record of Russia and China and see what we can do to have everyone do what they can to tighten the noose around the Iranian regime."

"I think that we let Russia and China off the hook," said the lawmaker, who added she thinks Iran "overplays its hand" and exaggerates the progress made by its nuclear program.

"I think that it's not too late. I think that we still have the power to change what is happening," she said.

Early this month, Ros-Lehtinen directly accused China of "eagerly expanding trade" with the Islamic republic and of being a "key ally and protector of Iran that has made clear that it will prevent significant pressure on Tehran."

She said China's purported help in facilitating North Korea's shipments of advance missiles and chemical weapons ingredients to Iran was a direct violation of UN Security Council sanctions resolutions.