President Faustin-Archange Touadera controls only a fraction of the country, most of it overrun by militants who claim to protect either the Christian or Muslim communities.
Touadera, addressing the annual United Nations General Assembly session, urged a complete lifting of the arms embargo on the country. Russia has already received an exemption.
Onanga-Anyanga said that the need for weapons was "undeniable" as the CAR central government builds its own armed forces to the tune of 1,300 troops annually through 2023.
"It's dangerous to have trained men loafing around all day. If they aren't under supervision and put to use, they risk being drawn back to the demons of the past and returning to predation," he said.
Onanga-Anyanga also acknowledged the "need for the clearest transparency."
He said that the head of the UN sanctions committee would travel on October 2 to Bangui to "examine the needs and make sure that these transactions are in line with the positions of the Security Council."
Risking diplomatic 'cacophony'
Thousands of people have died, 700,000 have been internally displaced and another 570,000 have fled abroad in fighting since 2013, when majority-Muslim militias toppled longtime leader Francois Bozize, a Christian.
Russia, along with sending weapons, has proposed mediating with rebel groups in CAR in a sign of Moscow's growing post-Cold War ambitions in the continent.
Former colonial ruler France has rejected the Russian initiative, saying that there was "no alternative" to the process led by the African Union.
"There must absolutely be coordination among partners," he said of the political mediation.
"For it to be constructive, everyone needs to have the same vision and approach," he said.
"Solitary, non-coordinated moves could create a real cacophony."
He supported Russia's decision to join as an observer in the African Union mediation mission along with France and the United States.
The UN stabilization force in Central Africa has 12,000 troops and 2,000 police officers.
Nearly a year ago, the UN Security Council authorized boosting the number by 900 military personnel, although Onanga-Anyanga admitted that the level had not yet been reached.
He said that troops from Rwanda and Nepal had arrived but did not yet have equipment in place.
Since its establishment in 2014, the UN peacekeeping force known by its French acronym MINUSCA has witnessed the deaths of 70 soldiers.