Equity markets in Asia are giving up some of their gains made after news of a ceasefire in Iran, as profound uncertainty remains over the future of the agreement and whether ships will be allowed to freely transit the Strait of Hormuz, CNN reports.

On Thursday, Hong Kong’s Hang Seng index opened down 0.6% while China’s Shanghai Composite index declined 0.6% as of 10:15 am local time. South Korea’s Kospi also fell 1.11%, while Japan’s benchmark index Nikkei 225 was trading 0.6% down.

Meanwhile, US West Texas Intermediate crude futures rose 2.6% to $96.89 a barrel and Brent crude futures, the global benchmark, rose 2.1% to $96.75 a barrel.

Thursday’s moves are a slight reversal from the initial market reaction to the two-week ceasefire that US and Iran announced this week. On Wednesday, US crude prices plunged 16.4%, while the Dow had its best day in a year. The two nations are expected to continue negotiations in Islamabad, Pakistan, starting Saturday.

However, the fragile peace has already encountered some snags. Iran’s Islamic Revolutionary Guard said shipping through the Strait of Hormuz had stopped following Israeli strikes in Lebanon, which it considered a violation of the ceasefire agreement.

The US and Israel’s war against Iran—and the effective closure of the crucial Strait of Hormuz—has caused the biggest oil supply shock on record, choking off roughly 12 million to 15 million barrels of crude oil a day.

Analysts have warned that it will take months for the disruption caused by more than a month of fighting to subside. Meanwhile any further conflict could continue to have an inflationary effect on oil prices.