TransCanada Corp (TRP.TO) launched an open season on Thursday for additional commitments for the transportation of crude oil on the Keystone pipeline system, according to a company statement.

The open season will close on Sept. 28.

The Keystone system, including the Keystone and Keystone XL pipelines, moves oil from Hardisty, Alta., to markets in Cushing, Okla., then onto the U.S. Gulf Coast.

While the original Keystone is already operating, the controversial Keystone XL was delayed for years before being rejected by the administration of former U.S. President Barack Obama.

In May, TransCanada's chief executive said lower oil prices and alternative export routes were complicating negotiations for shipper commitments on the XL pipeline project. He said the company did not have a firm deadline for concluding those talks.

In March, President Donald Trump's administration approved Keystone XL. The expansion increases the capacity of the current Keystone system from Canada's oil-producing Alberta province to the Gulf of Mexico.