The U.S sanctioned a network of Iranian companies worth billions on Tuesday, including banks and funds accused of financing the country’s paramilitary apparatus. Washington’s move increases pressure on Tehran, sending a message to governments and companies still working with Iran to stop or face penalties.

The U.S.’s goal in targeting the Basij militia’s financing network, emphasizing the network’s use of child soldiers and other humans rights abuses in its announcement of the sanctions, is to undermine the financing of the prominent Islamic Revolutionary Guard corps unit and disincentivize the doing of business with the nation.

“The IRGC is pervasive within the Iranian economy,” a senior administration official said. “This is precisely the kind of activity that we have warned other companies and governments about extensively.”

Firms are leaving Iran as the U.S. increases sanctions meant ensure Tehran renegotiates a new nuclear and security deals that addresses Trump administration concerns, writes the Wall Street Journal.

Companies and governments in China and Europe may still trade with Tehran in order to have access to the country’s oil – effectively amounting to an opposition to Washington’s having left the 2015 Iran nuclear deal.

U.S. Treasury sanctions claim Basij’s ownership of banks and companies spans across the entire Iranian economy. These entities are subject to U.S. sanctions effective November 5 – the second phase in Washington’s new pressure campaign meant to cut Iran from financial and trade ties to the world.

Human-rights groups condemned the sanctions, which were announced on Tuesday. The European Union and other Western governments blacklisted the sanctions. Companies or banks could face U.S. penalties for preserving ties with Iran.

Alireza Miryousefi, spokesman for Iran’s mission to the United Nations, called the sanctions a “unilateral campaign of bellicosity against Iran.”

The Treasury says Mehr Eqtesad Bank is integral to the Basij network. U.S. officials claim it provides hundreds of millions of dollars to the militia’s foundation through dividends and interest-free credit lines.

Bank Mellat, which in part financed Iran’s nuclear program, sent similar amounts to Mehr Eqtesad Bank, claims the U.S..

“This vast network provides financial infrastructure to the Basij’s efforts to recruit, train and indoctrinate child soldiers who are coerced into combat under the IRGC’s direction,” U.S. Treasury Secretary Steven Mnuchin said. “The international community must understand that business entanglements with the [Basij] network and IRGC front companies have real world humanitarian consequences.”

A senior U.S. official added: “We’re going to make sure, whether it’s through SWIFT or through other means, that sanctions are enforced. If there are prohibited transactions, going through SWIFT or any other entity, we’re going to make sure we enforce those sanctions quite vigorously.”