Is President Donald Trump's approval of the hotly disputed Keystone XL pipeline good or bad for oil and gasoline prices?

The simple answer is we don't know yet.

At least some analysts and U.S. oil producers worry the project could further depress prices by adding more crude to an already oversupplied global market.

Opposed by the Obama administration over environmental concerns, TransCanada's Keystone XL would bring heavy crude from Canadian tar sands to Steele City, Nebraska. From there, it would link up with an existing pipeline and send the oil to refineries on the Gulf Coast.

A big question is what happens to the fuel after that.

The United States will probably end up shipping much of the refined oil to Asia or Europe in the form of gasoline and other fuels. But forecasts for oil demand are not currently increasing enough to absorb rising U.S. fuel exports, so there is a risk that refined Canadian crude gets stuck in already brimming U.S. storage tanks.

Canadian tar sands oil is already moving by rail, so completion of the 800,000-barrels-a-day Keystone XL pipeline would not necessarily cause a huge surge in output. But it would support planned production increases from Canadian fields and make transportation more efficient.