Increasing concerns about a conflict between the US and Iran hit equity markets on Tuesday and sent gold prices to a fresh six-year high, jolting investor confidence days ahead of crucial trade talks between US President Donald Trump and his Chinese counterpart Xi Jinping.

The latest round of sanctions against supreme leader Ayatollah Ali Khamenei and military top brass meant the “permanent closure of the path to diplomacy”, the Islamic republic’s foreign ministry said.

Trump unveiled the new restrictions on Monday, days after the downing of a US drone that Tehran said had entered its airspace.

The Iranian tweet, from ministry spokesman Abbas Mousavi, provided a catalyst to sell for Asia stock traders, who had been sitting on their hands ahead of the Trump-Xi meeting at the end of the week.

Hong Kong fell more than one per cent, while Shanghai was 1.7 per cent off and Tokyo dropped 0.6 per cent, with profit-taking after a recent rally adding to selling pressure.

Sydney was down 0.1 per cent, Seoul and Singapore each retreated 0.3 per cent and Taipei lost 0.8 per cent. Still, Wellington, Manila, Bangkok and Jakarta were slightly higher. The Cambodia Securities Exchange index rose 0.5 per cent.

London fell 0.4 per cent in the morning, while Frankfurt and Paris each lost 0.3 per cent.

Safe-haven investments climbed, with gold breaking $1,430 for the first time since September 2013 and a softer dollar adding support, while the yen – a go-to unit in times of turmoil – was up against the greenback.

Traders were also keeping tabs on developments in the China-US trade standoff as the leaders prepare for crunch talks on the sidelines of the G20 Summit in Osaka.

World markets have rallied since Trump last week flagged positive phone talks with Xi and said they would discuss their trade spat.

On Tuesday, Chinese state media said top-level negotiators for both sides had held discussions ahead of the meeting, and “exchanged opinions on economic and trade issues”. The call took place “at the request of the US side” and they agreed to maintain contact, Xinhua News Agency said.

“The G20 will not get going until midweek, but the anticipation of a meeting between the leaders of China and the US is keeping markets guessing,” said Oanda senior market analyst Alfonso Esparza.

“The prolonged trade war between the two largest economies has downgraded global growth as more barriers to trade means higher prices. Optimism remains high, but more details need to emerge before the market can fully price in how far apart the two sides really are.”

Despite the rising fears of conflict between the US and Iran, crude prices extended the morning’s losses, with David Madden, market analyst at CMC Markets UK, saying “traders began to fear that demand for oil will fall”.

Iran and the US have said they do not want a war, with the US content with trying to cripple Iran economically.

Oil traders are also keenly awaiting a meeting of Opec and other major producers this weekend, hoping for clarity on their output reduction programme, which has supported prices.

The greenback was down against most other currencies, weighed by expectations the US Federal Reserve will cut interest rates as soon as July, while bitcoin held above $11,000 after breaking the marker for the first time in 16 months.