The price of a barrel of Brent crude oil, the international standard, has topped $100 a barrel again, jolting markets just days after it spiked near $120.

Iran escalated attacks on parts of Dubai and shipping assets, pushing oil prices above $100 a barrel and causing more concern about the length of the Middle East war and the effective closure of the Strait of Hormuz.

The ongoing American-Israeli war with Iran, for all its complexity and global effects, boils down to a single question: Who can take the pain the longest? A surge in oil prices points to what may be Iran’s most effective weapon and the United States’ biggest vulnerability in continuing the campaign: Damaging the world economy.

Markets on Wall Street retreated and oil prices jumped another 5% again early Thursday as the war in Iran approached its second week with no indication that the United States and Israel were ready to scale back their attacks.

Iran might be outgunned and outspent by the US and Israel but it has one major advantage — its control over the Strait of Hormuz.

Iran’s parliament speaker said Thursday that any invasion of Iran’s islands will “make the Persian Gulf run with the blood of invaders.” It wasn’t immediately clear what prompted Mohammad Bagher Qalibaf’s comments,

The US and Israel’s war on Iran forced world governments to intervene to shore up energy supplies, even as President Donald Trump once again said fighting will end soon.

Goldman Sachs economists Manuel Abecasis and David Mericle in a new research note looked at the economic implications of the Iran war on the U.S. economy.