US congressman Henry Cuellar and his wife have been charged with accepting around $600,000 (£478,000) in bribes, the justice department says.
It is alleged the couple corruptly received money from an Azerbaijani government-owned oil company and a Mexican bank.
The Texas Democrat has denied the charges in a statement.
The couple were bailed after appearing in court in Houston. If found guilty, they could face decades in prison.
“I want to be clear that both my wife and I are innocent of these allegations,” Mr Cuellar, 68, said on Friday.
The couple are each charged with multiple counts of conspiracy, bribery, wire fraud, money laundering and violating a ban on acting as agents of a foreign organisation.
The justice department said bribes were laundered from 2014-21 via a series of “sham consulting contracts” through middlemen and front companies owned by Imelda Cuellar, 67.
In exchange for the money, the indictment alleges Mr Cuellar agreed to influence US foreign policy in favour of Azerbaijan and push measures beneficial to the bank headquartered in Mexico City, including changes to money-laundering laws and attempts to block regulation of the payday lending industry.
The Cuellars allegedly used the proceeds from the bribery schemes to pay off a number of debts and make purchases for their family.
Among the outgoings were more than $58,000 (£46,000) on credit card payments, some $11,000 in car payments, $18,000 at wholesale stores and $12,000 for a custom gown, according to the indictment.
Senator Robert Menendez, a New Jersey Democrat, faces similar charges. He and his wife are accused of taking bribes in exchange for the senator using his influence to benefit the governments of Egypt and Qatar.
In the statement released by his office, Mr Cuellar vowed to keep campaigning for re-election in November.
“Before I took any action, I proactively sought legal advice from the House Ethics Committee, who gave me more than one written opinion, along with an additional opinion from a national law firm,” he said.
“The actions I took in Congress were consistent with the actions of many of my colleagues and in the interest of the American people.”
Mr Cuellar was a lawyer and former customs broker before entering politics. He was first elected to Congress in 2004 and is a former co-chair of the Congressional Azerbaijan Caucus.
Hakeem Jeffries, Democratic party leader in the House of Representatives, said Mr Cuellar would take a leave of absence from his post on a homeland security subcommittee while the case continues.
Mr Cuellar’s home and campaign office in Laredo were raided in January 2022.
Authorities said at the time the raid was part of a federal investigation into Azerbaijan and US businessmen who have links to the country.
Mr Cuellar is widely considered a centrist and has been described as the lone anti-abortion House Democrat.
In 2022, he narrowly survived a primary challenge from a progressive candidate, Jessica Cisneros, who once worked as an intern in his office.
Source: BBC