U.S. President, Donald Trump, has signed executive orders that support two controversial oil pipelines, to the chagrin of environmentalists.

The new Republican president backed the Keystone XL and Dakota Access projects, on the condition that American steel is used.

The Obama administration had in late 2015 halted Keystone, which would carry crude from Canada to Texas.

The army decided in 2016 to explore other routes for the Dakota pipeline amid huge protests by Native Americans.

While oil producers in Canada and North Dakota are expected to benefit from a quicker route for crude oil to U.S. Gulf Coast refiners, a revival of the projects would mark a bitter defeat for Native American tribes and climate activists, who vowed to fight the decisions through legal action.

Trump campaigned on promises to increase domestic energy production and before taking office indicated he supported completion of the Dakota pipeline and re-starting the C$8 billion ($6.1 billion) Keystone XL project, which was rejected in 2015 by then-President Barack Obama.

Protesters had rallied for months against plans to route the $3.8 billion Dakota Access Pipeline beneath a lake near the Standing Rock Sioux reservation, saying it threatened water resources and sacred Native American sites.

It is not yet clear how exactly the orders will move the projects forward.