Sen. Tom Cotton (R., Ark.) warned European allies and international business community members against giving into Iran's "nuclear blackmail" on Wednesday as he marked the one-year anniversary of the U.S. withdrawal from the nuclear deal.

Cotton, who fiercely opposed the Obama administration's efforts to pass the deal, discussed the latest belligerent behavior out of Tehran in a speech on the Senate floor and wished the Islamic Republic's leaders a "Happy Anniversary."

"Just this morning, Iran threatened to renew its rush to the bomb, stockpiling more uranium and producing more heavy water, even threatening to enrich nuclear fuel to dangerous levels in the months ahead if the civilized world does not cave to its demands," Cotton said. "But we know better than to cave into the ayatollahs. The United States will remain steadfast in our pressure campaign against Iran until that regime abandons its nuclear and missile program and its support for terrorism."

"As for our European allies and partners, and members of the business community abroad, I hope Iran’s threats serve as a needed wakeup call. Any attempt to invest in Iran's market, under any circumstances other than Iran’s complete and verifiable cessation of its full range of malign activities, will be fraught with huge legal and financial risks. Huge risks," he added. "Businesses shouldn’t put themselves in that compromising position, and European partners shouldn’t give in to Iran’s high-stakes nuclear blackmail."

Cotton said the U.S. was standing up to Iran's "killing spree" across the Middle East under President Donald Trump, rather than acquiescing to it. He also ripped 2020 Democratic candidates who have spoken about re-entering the agreement if they reach the White House.

"Iran is a weaker adversary today than it was a year ago, when it was flush with bribe money from its nuclear deal with the Obama administration," Cotton said. "But not everyone sees it that way. At least six Democratic presidential candidates have talked about re-entering this outdated, obsolete nuclear deal with Iran. They would give the Ayatollah and his armies sanctions relief yet again, at a time when Iran's economy is on the mat."

Cotton announced a resolution reaffirming U.S. policy to never allow Iran to build nuclear weapons, as well as saying sanctions on the regime won't be waived until it stops sponsoring terrorism and dismantles its ballistic missile program.

Cotton recalled the flak over an open letter he and 46 other Senators sent to Iranian leaders in 2015, telling them the nuclear deal with the Obama administration wouldn't be "worth the paper it was printed on" unless it was ratified as a treaty by two-thirds of the U.S. Senate. Otherwise a new president could wipe it away without congressional approval.

The New York Daily News melodramatically labeled Cotton and fellow lawmakers "traitors," and a debate over whether Republicans had violated the oft-discussed but almost never-enforced Logan Act ensued.

Despite its unpopularity, the nuclear deal was enacted, but Cotton noted with satisfaction that he and his fellow letter-writers were vindicated when Trump "did revoke that deal with the stroke of a pen."

Trump announced Tuesday that the U.S. will put forward "tougher sanctions than ever" over Iran's continued nuclear buildup and sponsorship of terrorism. Relations between the U.S. and Tehran have bottomed out as the Trump administration continues enacting measures to squeeze the country's already struggling economy.