The United States has eliminated the last of its declared chemical weapons stockpile, the government announced on Friday.

"Today, I am proud to announce that the United States has safely destroyed the final munition in that stockpile — bringing us one step closer to a world free from the horrors of chemical weapons," US President Joe Biden said in a statement.

The last remaining rockets filled with the GB nerve agent (sarin) were destroyed by workers at the Blue Grass Army Depot in Kentucky last month, as were munitions containing mustard gas at the Pueblo Chemical Depot in Colorado.

"Though the use of these deadly agents will always be a stain on history, today our nation has finally fulfilled our promise to rid our arsenal of this evil," Senate Minority Leader Mitch McConnell said earlier.

Global declared stockpiles 'irreversibly destroyed'

The global chemical weapons watchdog said the US was the last "possessor state" and its announcement on Friday means that all declared chemical weapons stockpiles globally have now been "irreversibly destroyed."

"The end of destruction of all declared chemical weapons stockpiles is an important milestone," said Fernando Arias, head of Organization for the Prohibition of Chemical Weapons. 

However, the Hague-based watchdog said it would remain vigilant after incidents in recent years where chemical weapons were used in Syria as well as by Russia.

"Recent uses and threats of use of toxic chemicals as weapons illustrate that preventing re-emergence will remain a priority for the organization," Arias said.

Chemical weapons around the world

Chemical weapons were first used on a large scale during World War I with devastating consequences.

The US had a deadline of September 30 to eliminate its remaining chemical weapons under the Convention on the Prohibition of Chemical Weapons that was implemented 26 years ago.

There were 193 signatories to the 1997 agreement, with abiding countries promising to never use chemical weapons and to destroy all chemical weapons stockpiles. 

North Korea, Israel, Egypt and South Sudan are some of the countries which have not signed on to the agreement. 

By destroying the munitions, the US sends a message that chemical weapons are no longer acceptable in the battlefield.

"It shows that countries can really ban a weapon of mass destruction," said Paul F. Walker, vice chairman of the Arms Control Association and coordinator of the Chemical Weapons Convention Coalition.

"If they want to do it, it just takes the political will and it takes a good verification system." 

zc/wd (AP, AFP, Reuters, dpa)