(Adds details on crude swap from Pemex and oil traders)
By Ana Isabel Martinez
MEXICO CITY, Oct 28 (Reuters) - State oil firm Pemex said on Wednesday it had received a license from the United States to import U.S. light crude in exchange for exports of Mexico's heavier crude oil for the first time, albeit with a lower ceiling than originally planned.
The terms of the year-long license will allow Pemex's commercial arm, P.M.I. Comercio Internacional, to import U.S. light crude to process in its refineries from October, with the limit capped at 75,000 barrels per day (bpd).
Pemex will initially receive conventional U.S. light crudes as part of the swap and later shipments could carry shale crudes as well.
A Pemex spokesman said the decision to cut the original plan to import up to 100,000 barrels per day was made in accordance with the company's present needs at its refineries.
The first U.S. shipment would arrive in Mexico from the first half of November, he said.
"The permit is for 75,000 (bpd) because that's what we asked for," he said. "They gave us permission for 75,000 (bpd) for one year, but when that year ends, we can ask for more or less, whatever we need."
The spokesman said it was not a like-for-like deal, and that Mexico was not obliged to export an additional 75,000 bpd to the United States.
Pemex director of corporate partnerships and new business, Jose Manuel Carrera, said in a radio interview that up to 27 million barrels of imported U.S. oil would be processed in Mexican refineries over the course of the year.
"The Mexican crude we would no longer be processing, obviously that would be destined for export in markets where it has higher value, where it can be processed more efficiently," Carrera said.
In August, the United States decided to allow sales of crude for processing in Mexico for the first time, a milestone in loosening a contentious ban on exporting domestic oil.
Refining companies in the U.S. Gulf Coast will keep processing Pemex's heavy Maya crude and they could also receive small volumes of medium Isthmus crude, according to oil market traders who spoke on condition of anonymity.
Maya is a better match for U.S. refiners than the deluge of light oil coming from Texas and North Dakota.
Under the terms of the deal, Mexico must refine all the U.S. crude received at home. Re-exports are forbidden.
Pemex has not said which firms will supply Mexico with crude, but traders said the likes of Phillips 66, Tesoro, Valero Energy, Chevron Corp., Royal Dutch Shell and ExxonMobil are able to refine Mexican heavies and deliver such light crudes.
Although limited in scope, the move toward freeing up trade will please U.S. oil producers such as Pioneer Natural Resources and ConocoPhillips, which say the restrictions force them to sell oil at below global market rates as shale oil boom created a glut of light crude.
It may also add momentum to efforts in the U.S. Congress to repeal a broader ban on U.S. oil exports, which critics see as a relic of the 1970s Arab oil embargo era. (Additional reporting by Veronica Gomez, Gabriel Stargardter, Marianna Parraga and Liz Hampton; Editing by Simon Gardner, Marguerita Choy, Grant McCool)