BEIRUT (AP) — Lebanon's leader on Saturday asked the United States to offer evidence to back up new sanctions against the former Lebanese foreign minister, who is an important political ally of the Iran-backed Hezbollah group.

President Michel Aoun asked the Lebanese foreign ministry to make the necessary contacts to secure any evidence and documents that prompted the U.S. Treasury sanctions on Gebran Bassil, who leads the largest bloc in parliament and is also the president's son-in-law.

The move against Bassil on Friday was a major expansion of the scope of U.S. sanctions targeting Hezbollah’s political partners in Lebanon. There were concerns that sanctioning Bassil, who is still an influential politician, would further complicate efforts to form a government in the country.

Lebanon is grappling with multiple economic and financial crises, and a deepened political impasse after the government resigned in August.

The U.S. Treasury designation did not mention Bassil’s alliance with Hezbollah, but the broadening sanctions appeared to be part of the Trump administration’s maximum pressure campaign against Iran and its allies.

Speaking to Lebanon’s LBC TV station late Friday, U.S. Assistant Secretary for Near Eastern Affairs David Schenker said it is possible to challenge the designation through the Treasury or the Office of Foreign Asset Control, but called the case solid.

“As you know these things are very difficult to do because the case is so solid. These designations take months to prepare, are reviewed by the interagency, by lawyers and are based on facts,” Schenker said. “He is welcomed to do so.”

Bassil leads the president's Christian political party, the Free Patriotic Movement, and has served as Lebanon's foreign minister, and minister of energy and telecommunications over the past 12 years.

Bassil was a prominent target of anti-government protesters who took to the streets last year against endemic corruption and state mismanagement in Lebanon. He is believed to have ambitions to run for the presidency himself.

The U.S. government designation, under the 2012 Magnitsky Act, said Bassil was “at the forefront of corruption” in Lebanon, was involved in “misappropriation of state assets" and "the expropriation of private assets for personal gain."

While minister of energy in 2014, Bassil was involved in approving projects that would have steered Lebanese government funds to individuals close to him through a group of front companies, the designation stated.

Because of the sanctions, Bassil will be denied entry into the United States and any assets he owns there would be frozen.

Bassil is not the first Lebanese official to face U.S. sanctions. The United States has been sanctioning Hezbollah officials for years, and recently began targeting politicians close to the group. In September, the Treasury imposed sanctions on two former Lebanese Cabinet ministers allied with the militant group in a strong message to Hezbollah and its allies who control majority seats in Parliament.

Aoun also sought clarifications for the “circumstances” leading to those accusations, but didn't demand evidence.

Aoun said the U.S. evidence and documents against Bassil should go to the Lebanese judiciary. Aoun said he would personally oversee the case, including bringing it to court when and if necessary.

The independence and integrity of Lebanon’s judiciary is widely seen as being compromised by the influence of the ruling sectarian parties. Four months after the massive explosion that devastated Beirut’s port and parts of the city, no senior government official or minister was named for probing, despite questions over their collective role in covering up the presence of enormous amounts of dangerous chemicals stored at the port.

Immediately after the announcement of U.S. sanctions, Bassil tweeted that the designation didn't frighten him.

The FPM, Bassil's party, said the accusations against him were a “blatant defamation” and “the use of U.S. laws to take revenge of a political leader for refusing to go against his principles and national choices and convictions.” It was an apparent reference to Bassil's alliance with Hezbollah.

Hezbollah called Bassil's designation purely political and a blatant interference in Lebanese affairs.