After a weak lead from Wall Street on Friday, markets were looking to a string of US data in the week ahead for clues about the health of the world's largest economy, with figures due out on housing, consumer confidence and GDP growth.
In Tokyo the benchmark Nikkei-225 index fell 0.19%, or 27.99 points, to close at 14,837.68. Seoul lost 0.45%, or 8.78 points, to end at 1,949.05 and Sydney closed a marginal 0.03%, or 1.5 points, higher at 5,440.2.
Hong Kong shares were down 1.13% in afternoon trade, while on the Chinese mainland, shares extended losses in the afternoon on worries about a possible tightening of credit to the property sector.
Shanghai was down 1.76% while the Shenzhen Composite Index, which tracks stocks on China's second exchange, fell 1.11%.
Domestic banks have recently tightened lending to the real estate sector, state media reported last week, though some lenders denied any such move.
"We're mostly focused on news from local news media that big banks are stepping back on loans in the sector," Shenyin Wanguo Securities analyst Qian Qimin told Dow Jones Newswires.
However, any impact from property loan curbs would likely be limited, Qian added.
The world's biggest economies vowed on Sunday to boost global growth by more than $2 trillion over five years, shifting their focus away from austerity as a fragile recovery takes hold.
The G20 members said they aim to lift their collective GDP by more than two percentage points over the next five years.
However, investors appeared to be focusing more on the forthcoming US figures, as analysts suggested the data may disappoint.
US February consumer confidence figures are due to be released on Tuesday, followed by data showing durable goods orders and initial jobless claims on Thursday. On Friday, the final estimate for fourth-quarter US gross domestic product is out.
"It is possible that data to be released this week could come out lower than expected. Caution is needed over continued worries about the possibility of a US slowdown," Tsuyoshi Nomaguchi, a senior strategist at Daiwa Securities, said in a note to clients.
Mr Nomaguchi said the US market could receive support from investors hopeful that weak data could encourage the US Federal Reserve to continue its zero interest rate policy.
Japan will also publish a string of data, including inflation figures, on Friday.
US stocks finished the week with modest declines. The Dow Jones Industrial Average fell 0.19%, or 29.93 points, to 16,103.30 on Friday.
The broad-based S&P 500 dropped 0.19%, or 3.53 points, to 1,836.25, while the tech-rich Nasdaq Composite Index slipped 0.10 percent or 4.13 points to 4,263.41.
On currency markets, the dollar stood at 102.30 yen in afternoon trade in Asia, down from 102.49 yen in New York Friday.
The euro was at $1.3739 and 140.57 yen, compared with $1.3734 and 141.00 yen.
Oil prices rebounded in Asia on strong US demand, driven by prolonged sub-zero temperatures across much of the country and geopolitical worries.
New York's main contract, West Texas Intermediate for April delivery, gained 29 cents to $102.49 in afternoon Asian trade, while Brent North Sea crude for April rose 20 cents to $110.05.
Gold fetched $1,327.33 an ounce at 0650 GMT, after hitting $1,332.45 late Friday — the highest point since Oct 31 — driven by strong Asian demand.
In other markets, Wellington closed up 42.01 points, or 0.85%, to end at 4,969.65 on positive earnings results. Freightways rose 2.84% to NZ$4.70 and Sky Network Television City soared 5.74% to NZ$6.08.
Taipei fell 0.48%, or 41.25 points, to 8,560.61.
Taiwan Semiconductor Manufacturing Co was 0.47% lower at NT$107, while Cathay Financial Holdings shed 3.04% at NT$44.7.