In Hong Kong, the benchmark Hang Seng Index opened down 16 points, or 0.07 percent, at 24,826.
The China enterprises index opened down three points, or 0.04 percent, at 8,372 while the tech index opened flat at 4,765.
Up north, the benchmark Shanghai Composite Index opened down two points, or 0.06 percent, at 4,094.
The Shenzhen Component Index was 52 points, or 0.34 percent, higher at 15,584 while the ChiNext Index was up 0.79 percent at 4,065.
In Tokyo, the Nikkei 225 Index opened 28 points, or 0.04 percent, down, at 69,288 before extending losses to be 108 points, or 0.16 percent, lower at 69,209 at one stage before noon.
In Seoul, the Kospi Composite Index opened up 150 points, or 1.76 percent, at 8,696 before the benchmark drifted down to hover at 8,692 at one stage before midday.
The markets settled into a more measured tone on Gulf developments as the initial excitement over the preliminary agreement between Washington and Tehran began to fade.
Oil prices, which settled at a three-month low overnight, reflected the cautious stance, with Brent crude futures up 0.1 percent at US$83.25 a barrel.
Shippers in Asia and Europe said rebuilding confidence in resuming transit through the Strait of Hormuz could take weeks.
“While it is an important diplomatic breakthrough that should remove a key source of market volatility, the durability of the deal is likely to be tested in the future,” Westpac analysts wrote in a research note.
“Many sticking points, including the fate of Iran’s nuclear programme, were left to be resolved in subsequent negotiations.” (Reuters/Xinhua)
