The outgoing administration of US President Donald Trump has imposed more Iran-related sanctions on an entity and an individual, as Iran reasserts its position that the 2015 nuclear deal is not open to renegotiation and that the next US administration has to observe the agreement and the UN resolution that endorses it.

The US Treasury Department in a statement said on Thursday that it had imposed sanctions on Shahid Meisami Group and its director, making baseless accusations against them.

The Treasury accused them of being involved in a so-called chemical weapons research program and linked to the Iranian Organization of Defensive Innovation and Research, which is sanctioned by Washington.

"Iran�s development of weapons of mass destruction is a threat to the security of its neighbors and the world,� Treasury Secretary Steven Mnuchin said in the statement.

He added that the United States will continue to counter any efforts by the Iranian government �to develop chemical weapons� that may be used by it or �its proxy groups to advance their malign agenda.�

Iran has denounced the US for adopting a double-standard policy toward the use of Weapons of Mass Destruction (WMDs), reminding Washington of its support for slain Iraqi dictator Saddam Hussein in his war on Iran in the 1980s.

Leader of the Islamic Revolution Ayatollah Seyyed Ali Khamenei has issued a fatwa (religious decree), which bans the development and production of weapons of mass destruction, including nukes, as contrary to Islam.

During the Iraqi-imposed war, "Iran was not even allowed to use the most basic equipment and facilities like barbed wires, while the other side was provided with the most modern war equipment and even chemical weapons,� the Leader said.

Hundreds of thousands of Iranians were killed in the eight-year war Saddam imposed on Iran and many more were affected by the chemical weapons like mustard gas used by the Iraqi regime.

Iran�s Sardasht, in West Azerbaijan province, was the third populated city in the world, after Japan's Hiroshima and Nagasaki, to be deliberately targeted with weapons of mass destruction. It was also the first city in the world to be attacked with poisonous gas.

Thanks to the support offered by the US and other Western states, Iraq once possessed a huge arsenal of chemical weapons.

Reports say the CIA knew about Iraq�s use of chemical weapons as early as 1983, but the US took no action against the violations of international law, and even failed to alert the UN.

The Trump administration returned the sanctions in 2018 after leaving a historic and internationally-lauded nuclear agreement between Iran and world powers.

Departure from the deal -- that is officially known as the Joint Comprehensive Plan of Action -- and restoration of the bans both constituted illegal actions because they came in absolute disregard for the fact that the JCPOA has been ratified by the United Nations Security Council. The illegal measures were also marked by sheer unilateralism as they violated the international nature of the deal that has the UK, France, Russia, and China plus Germany as its other parties.

In September, the United States imposed unilateral sanctions against Iran after it had failed to garner support for its anti-Iran move at the United Nations.

US Secretary of State Mike Pompeo said the sanctions would target Iran�s Defense Ministry and the country�s Atomic Energy Organization on September 21, a day after Washington unilaterally declared that all UN sanctions against Tehran were re-instated.

Pompeo announced that all UN sanctions against Iran were "back in effect" under the �snapback� provision in the JCPOA.