Most Asian emerging currencies fell on Monday as the US dollar held steady, while heightened tensions in the Middle East pushed oil prices higher.

The dollar index was barely changed at 97.171 after gaining 0.35 per cent last week, but the greenback broke above 108 yen to hit its highest since Wednesday, still in the middle of the 107-109 range where it has traded for a month.

Underpinning the dollar, investors on Friday tempered expectations for deep US interest rate cuts later this month, though a quarter-point cut is still widely expected.

Brent crude futures were up 51 cents, or 0.8 per cent, at $62.98 a barrel by 6:12 am after a British tanker was seized by the Iranian military at the end of last week.

Any rise in oil prices puts pressure on major importers of the commodity in the region such as India, Indonesia and Thailand.

The dollar would hold the upper hand in Asia this week and the "jittery risk environment" surrounding Iran tensions could further impinge on the Asian currencies, OCBC Bank analysts said in a note on Monday.

The Indian rupee fell as much as 0.4 per cent to a near three-week low, while the Indonesian rupiah slid as much as 0.3 per cent to 13,965 against the dollar.

The Thai baht lost up to 0.3 per cent. The currency was little fazed by trade data which showed June exports fell 2.15 per cent year-on-year, smaller than the Reuters poll forecast of 5 per cent drop.

Exports, the main driver of Thai growth, declined for a fourth straight month in June.

The South Korean won also depreciated, shedding up to 0.4 per cent to 1,179.10 against the dollar, as the export-oriented economy's shipments for the first 20 days of the month fell a sharp 13.6 per cent from a year earlier, according to customs data.

Semiconductor products, which make up for about one-fifth of the country's total exports, suffered a 30.2 per cent drop in overseas shipments, the Korea Customs Service data showed.

Meanwhile, the Chinese yuan inched up 0.06 per cent on investor hopes that Sino-US trade tensions may be easing.

Some Chinese companies are seeking new purchases of US agricultural products, China's official Xinhua news agency said on Sunday, citing authorities, and investors widely take these kind of developments as gestures of goodwill between the world's two largest economies to end the year-long trade war.

The Malaysian ringgit and the Philippine peso were little changed.