Iran sought to obtain illicit nuclear weapons technology as recently as 2018, according to new disclosures by German intelligence that reveal how Tehran tapped black weapons markets without the knowledge of international nuclear inspectors tasked with performing oversight on the Islamic Republic's weapons sites as part of the landmark nuclear agreement.

The disclosures come against the backdrop of Iran's weekend attack on Saudi Arabian oil sites, which sparked international backlash and prompted Tehran to warn the United States of "all-out war" if it engages in retaliatory strikes on the Islamic Republic.

With tensions escalating, the German intelligence report issued Wednesday provides grist for congressional Iran hawks seeking to pressure the Trump administration into increasing its already tough economic sanctions on Tehran.

"In particular, states such as Iran, North Korea, Pakistan, and Syria attempted to acquire and redistribute such weapons in the context of proliferation, for example by concealing transport routes via third countries," the German-language report states, according to the Jerusalem Post‘s Benjamin Weinthal, who first reported its existence.

"Against this background [of proliferation], weapons of mass destruction continued to be a powerful political instrument during the reporting period, which could shake the stability of an entire state structure in both regional and international crisis situations," the report says.

Iran continues to seek the technology and know-how to quickly enrich uranium, the key component in a nuclear weapon, using advanced centrifuges.

"An example of this is the field of electrical engineering combined with the use of centrifuges in the process of uranium enrichment," according to the report. "Here, again and again, there are suspicions that foreign intelligence services put pressure on their own visiting scientists to obtain the desired technical know-how."

Iran, Pakistan, and North Korea are the primary culprits in this high-stakes nuclear proliferation effort.

"It is essentially the Islamic Republic of Pakistan, the Islamic Republic of Iran, the Democratic People's Republic of Korea [North Korea], and the Syrian Arab Republic need to be mentioned," German intelligence found. "The intelligence services of these countries, in many ways, are involved in unlawful procurement activities in the field of proliferation, using globally oriented, conspiratorial business and commercial structures."

Meanwhile, Iran continues to ratchet up its military threats against the United States and its regional allies following the weekend attack by the Iranian-armed Houthi rebels in Yemen.

In a memo sent to the Trump administration via the Swiss embassy, which handles diplomacy between Tehran and the United States, Iran vowed a "rapid and crushing" response to any American retaliatory attack, which President Donald Trump has been contemplating.

"Iran monitors, with full preparedness, any intention and move for the purpose of aggression against the country or the interests of the Islamic Republic and will give a decisive and all-out response to possible mischiefs in the harshest way which can surprise the aggressors," Ali Shamkhani, the secretary of Iran's Supreme National Security Council, was quoted as saying on Wednesday.