Giuliani did not respond to a request for comment | Sarah Rice/Getty Images Giuliani took money from Qatar, Venezuela, Iranian exiles His foreign clientele could present conflicts of interest as secretary of state.

Rudy Giuliani's paid consulting for foreign governments would present conflicts of interest as the nation's top diplomat that would make the Clinton Foundation look trifling.

Since leaving the New York mayor's office, Giuliani has made millions as a lawyer and consultant, including for some clients at odds with U.S. foreign policy. When some of those ties surfaced amid Giuliani's own presidential bid in 2007, they were considered to pose an unprecedented number of ethical quandaries for a potential commander in chief.

Now those concerns have no doubt been eclipsed by Donald Trump's own web of business entanglements, which are still not completely known to the public. Giuliani's participation in Trump's transition and contention for the job of secretary of state poses a direct challenge to Trump's promises to root out Washington self-dealing and ban his administration's officials from lobbying for foreign governments.

In 2011, an exiled Iranian political party called the Mujahedin e-Khalq, known as the MEK, paid Giuliani to give a speech in Washington calling on the State Department to remove the group from its list of terrorist organizations. The MEK recruited a host of other formal officials to its cause and succeeded in reversing the terrorist designation in 2012.

A subsidiary of Giuliani's consulting firm, Giuliani Partners, advised Qatar's state-run oil company on security at a natural gas plant, The Wall Street Journal reported. Qatar is a U.S. ally that hosts a major American military base but once stifled an attempt to arrest Khalid Sheikh Mohammad, who went on to mastermind the Sept. 11 attacks, according to the 9/11 commission report.

The same subsidiary, Giuliani Security & Safety, provided security advice to a Singapore gambling project on behalf of a partnership that included a tycoon close to the North Korean regime who is considered an organized crime figure by the U.S., according to a report in the Chicago Tribune. "I think the person involved, if it's correct, was a 1 percent owner that had no involvement with us, we never worked for, had nothing to do with," Giuliani told NBC's Tim Russert at the time.

Giuliani Partners also advised TransCanada, which sought to build the Keystone XL pipeline that President Barack Obama rejected but Trump has said he wants to approve. And Giuliani helped the maker of the OxyContin painkiller, Purdue Pharma, settle a Drug Enforcement Administration investigation with a fine.

The Houston-based law firm Giuliani joined as a named partner in 2005 lobbied in Texas for Citgo, the U.S. subsidiary of the Venezuelan state oil company then controlled by President Hugo Chavez, The New York Times reported in 2007. The firm also did work for Saudi Arabia's oil ministry, according to The Associated Press.

The law firm, Bracewell & Giuliani, lobbied at the federal level during Giuliani's time there for energy companies including Southern Company, Duke Energy, Energy Future Holdings, Arch Coal, Chesapeake Energy and NuStar Energy, records show. It also represented Cornell Companies, a private prison operator that later merged with GEO Group. Giuliani never personally registered as a lobbyist. He left the firm for rival Greenberg Traurig this year, and currently is on leave.

Giuliani's assistant at Greenberg Traurig and the Trump transition didn't answer requests for comment.

The Clinton Foundation has been hounded by Republican suspicions of selling access to Hillary Clinton as secretary of state, and the nonprofit did accept big bucks from foreign governments. But Clinton's defenders point out there's no proof she ever made an official act to benefit a foundation donor, and, unlike Giuliani, she never personally profited from the foreign contributions to her charity.

When Giuliani ran for president, he reported assets of $18.1 million to $70.4 million.