“Our financial system should not provide the rich, the powerful and the corrupt with the opportunity to shield their assets and avoid paying their fair share or with the opportunity to hide any illicit activity,” said Wally Adeyemo, the deputy national security adviser for international economics. “Nobody should be able to play by a different set of rules.”

The statement by the Panama Papers source was released through the German newspaper Süddeutsche Zeitung, which originally received the once-confidential archive of documents taken from the Panama-based law firm Mossack Fonseca. Bastian Obermayer, a reporter for the newspaper who received the original leak with his colleague Frederik Obermaier, wrote in a blog post that he had confirmed via encrypted chat that the statement had come from the same person — of unknown nationality — who provided the secret documents.

Süddeutsche Zeitung, working with the International Consortium of Investigative Journalists, a Washington-based group comprising more than 100 news media organizations, published articles about the Panama Papers starting last month that have set off political furors and unsettled financial institutions around the world.

According to the consortium, the documents reveal the hidden assets of 12 current and former world leaders, 128 other politicians and officials, and a range of sports figures and celebrities. The 214,000 shadow companies described in the documents are tied to people in more than 200 countries and territories. The papers include long chains of emails showing how the companies have been used.

News reports based on the documents have linked $2 billion in assets to a childhood friend of President Vladimir V. Putin of Russia, and disclosed the holdings of the Aliyev family, which has long held power in Azerbaijan. The prime minister of Iceland, Sigmundur David Gunnlaugsson, said he would temporarily step aside after the revelation that he and his wife owned an offshore company.

In the statement, the source denied being a government official or contractor, now or in the past. The confidential source was also extremely critical of the news media, suggesting that certain unnamed news organizations had declined initial offers to take and report on the documents.

The measures announced on Thursday by the Obama administration, which in most cases have been in the works for years, would attempt to combat illegal tax shelters with a collection of new tools.