The price of oil advanced past $99 US a barrel Tuesday, underpinned by political unrest in Egypt that raised fears of disruption to global crude supplies.

By mid-afternoon, benchmark crude for August delivery was up $1.55 to $99.54 a barrel in electronic trading on the New York Mercantile Exchange. The contract jumped $1.43 to close at $97.99 on Monday.

After massive weekend protests in Egypt that continued Tuesday, the country's military issued an ultimatum to President Mohammed Morsi that gives him 48 hours to meet the demands of the millions of Egyptians who have taken to the streets seeking his ouster.

The ultimatum, rebuffed by Morsi, raised worries on both sides that the military could outright take over, as it did after the 2011 ouster of autocrat Hosni Mubarak. It also raised the risk of a backlash from Morsi's Islamist backers, including his powerful Muslim Brotherhood party and hard-liners, some of whom once belonged to armed militant groups.

Unrest could affect supply route

Traders were concerned that the protests in Egypt and the civil war in Syria could affect the production and transport of oil supplies in the Middle East and North Africa.

"It is, above all, the risks to supply that are lending support to oil prices," said a report from Commerzbank in Frankfurt. "The situation in Egypt is threatening to escalate further. Although Egypt is not an oil exporter, the Suez Canal and a number of pipelines do make it an important transit route for oil from North Africa and the Gulf region."

Falling oil production in Libya and Nigeria was also seen as supporting prices.

Later in the day, investors will be monitoring fresh information on U.S. stockpiles of crude and refined products.

Data for the week ending June 28 is expected to show a draw of three million barrels in crude oil stocks and a build of one million barrels in gasoline stocks, according to a survey of analysts by Platts, the energy information arm of McGraw-Hill Cos.

The American Petroleum Institute will release its report on oil stocks later Tuesday while the report from the Energy Department's Energy Information Administration — the market benchmark — will be out on Wednesday.

In London, Brent crude was up 89 cents at $103.89 a barrel on the ICE Futures exchange.

In other energy futures trading on Nymex:

  • Natural gas gained 6.2 cents to $3.639 per 1,000 cubic feet.
  • Heating oil added 0.81 cent to $2.8817 per gallon.
  • Wholesale gasoline rose 2.35 cents to $2.7614 per gallon.