He said the decline in the ringgit's position was a source of concern to many, but the situation was outside the government's control.
Najib, who is also the Finance Minister, said of 149 world currencies, 123 faced a decline in value against the US dollar and Malaysia was not exempted nor the only country impacted.
He said three uncontrollable factors influenced the ringgit's value, namely "excessive speculation in the offshore market", the fall in oil prices and rise in US interest rates last December.
"With the measures taken by BNM, the market is convinced that the ringgit will be more stable and volatility curtailed to normal levels in the near term," he told the first monthly gathering of the Prime Minister's Department for 2017 here on Monday.
Najib also said there were signs of optimism and confidence that the Malaysian economy would recover positively this year after being faced with global challenges in 2016.
"Among the challenges was oil prices which are now at US$54 a barrel compared to US$44 last year.
"The price of palm oil is also at an encouraging level now, namely RM3,200 a tonne compared to RM2,600 last year, while rubber prices have also tripled. All this gives us the confidence that if we undertake vigorous initiatives, 2017 can be a successful year," he added.
Deputy Finance Minister Datuk Othman Aziz was reported previously as agreeing with bankers that the ringgit would recover to a fair value of 4.1 against the US dollar in the third quarter of 2017. - Bernama