The United States on Monday announced fresh sanctions targeting Iran’s nuclear program, underscoring Washington’s continued concerns over Tehran’s uranium enrichment activities despite ongoing diplomatic efforts to reach a new nuclear accord.

The latest sanctions target three Iranian individuals and an Iranian entity allegedly linked to the Organization of Defensive Innovation and Research (SPND), an institution widely believed to be at the heart of Iran’s nuclear research and weapons development infrastructure.

“Iran continues to substantially expand its nuclear program and carry out dual-use research and development activities applicable to nuclear weapons and nuclear weapons delivery systems,” U.S. Secretary of State Marco Rubio said in a statement released Monday morning.

Rubio noted that Iran remains the only non-nuclear weapons state in the world to enrich uranium to a purity of 60 percent—a level significantly above the 3.67 percent cap set by the 2015 Joint Comprehensive Plan of Action (JCPOA), the nuclear agreement that the U.S. abandoned in 2018 under then-President Donald Trump. Enrichment to 90 percent is typically considered weapons-grade.

The individuals sanctioned include senior officials allegedly playing key roles in Iran’s nuclear research efforts. Also targeted was an Iranian company, Fuya Pars Prospective Technologists, known alternatively as Ideal Vacuum, which the State Department said is affiliated with SPND.

According to the statement, Fuya Pars has actively sought to procure equipment from foreign suppliers and domestically manufacture technology that could be used in nuclear weapons development.

“These sanctions are designed to block Iran’s access to critical materials and technologies, and to disrupt the progress of its nuclear weapons-related activities,” the State Department added.

The sanctions freeze any U.S.-based assets held by the individuals and the company and prohibit American entities and individuals from conducting any business with them. The U.S. Treasury Department is expected to release further details regarding the specific roles of the sanctioned individuals later this week.

The announcement came just one day after the conclusion of the fourth round of diplomatic negotiations between U.S. and Iranian officials. The talks, held in Geneva, are aimed at drafting a new agreement that would prevent Iran from developing a nuclear weapon in exchange for economic relief.

Although no breakthrough was achieved during this round, both sides expressed cautious optimism about the prospects of continuing the dialogue.

A spokesperson for Iran’s Foreign Ministry criticized the move, calling the sanctions “counterproductive and politically motivated,” and reiterated Tehran’s position that its nuclear program is entirely peaceful and within its sovereign rights under the Nuclear Non-Proliferation Treaty (NPT).

The resumption of diplomatic engagement between the two longtime adversaries had raised hopes of reviving some form of nuclear agreement, but Monday’s sanctions highlight the challenges that remain.

Analysts say the Trump administration is walking a fine line, trying to pressure Iran into compliance while keeping the door open for a diplomatic resolution.

“The sanctions are meant to signal resolve, not a rupture,” said Dr. Lisa Quinn, a non-proliferation expert at the Center for Strategic and International Studies. “They reflect Washington’s skepticism, but not an end to negotiations.

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