The Kiwi dollar dipped against the United States currency following weak Chinese data.
Escalating tension between Saudi Arabia and Iran after the execution of a prominent Shiite cleric is also increasing demand for the greenback, a safe haven currency.
The New Zealand and Australian dollars sagged amid concern that China's economy remains anemic after a fifth month of contraction in factory activity.
Australia's dollar slid to 72.38 US cents, down 0.7 percent from December 31, while New Zealand's currency was 0.9 percent weaker since then at 67.71 US cents.
Japan's currency held its biggest monthly gain versus the dollar since January 2014 after Saudi Arabia cut diplomatic ties with Iran following an attack by protesters on its embassy in Tehran.
"The Saudi situation is, geopolitically, not good news," said Kengo Suzuki, chief currency strategist at Mizuho Securities Co. in Tokyo.
The Bloomberg Dollar Spot Index advanced 0.3 percent to 1,236.35. The yen was at 120.39 per dollar after earlier reaching 120.04. It touched 120.01 on Dec. 31, the highest since Oct. 22, and climbed 2.4 percent last month.
Caixin Media and Markit Economics release China's December manufacturing purchasing managers' index, and economists forecast it will show a 10th-straight month of shrinking.
The official purchasing managers index edged up to 49.7 last month from a three-year low of 49.6 in November, the National Bureau of Statistics said last Friday.
That was the official gauge's fifth month below 50 - the dividing line between contraction and expansion - the longest such streak since 2009.