Adds details throughout from interview

By Ernest Scheyder

HOUSTON, March 24 (Reuters) - Rio Tinto RIO.L aims to open Arizona's Resolution Copper mine by the mid-2030s but may need to export some of its copper concentrate due to the challenging economics of smelting in the U.S., a senior executive told Reuters on Tuesday.

The Anglo-Australian mining giant this month gained control of acreage needed to build one of the world's largest copper mines after a years-long court fight in which rising U.S. demand for the red metal clashed with the religious rights of the San Carlos Apache people.

"We are quite committed to bringing copper on as quickly as we can," Katie Jackson, head of Rio's copper business, told Reuters on the sidelines of the CERAWeek by S&P Global conference in Houston. "This is something we want to do in the early- to mid-2030s."

The Resolution project is slated to produce more than 40 billion pounds (18.1 million metric tons) of copper over its life and supply more than a quarter of U.S. demand.

With control of the acreage, Rio has now begun a $500 million drilling campaign to study the 30% of the deposit it previously could not access.

REFINING UNCERTAINTY

Resolution will produce copper concentrate that must be smelted into a form known as cathode that can be used to make wires and other products.

Rio executives have said for years the company aims to keep all of Resolution's copper inside the United States. Jackson on Tuesday, though, said "it's too early to say" whether all of the copper would remain.

Rio operates Utah's Kennecott copper mine and smelter and Freeport-McMoRan FCX.N operates the other U.S. copper smelter.

Jackson said that Rio has not shifted its policy on keeping Resolution copper in the U.S. but noted that smelting in the U.S. has become unprofitable.

Smelters make money by turning copper concentrate into metal for fees known as treatment and refining charges (TC/RCs), but those charges have turned negative in recent years due to a shortage of copper concentrate, meaning smelters are paying to process copper supplied to their plants.

Rio has been telling U.S. policymakers "that the current set of mechanisms and tariffs around copper don't solve that problem," Jackson said.

The Trump administration last year imposed a 50% tariff on semi-finished copper products, but left out copper input materials such as ores, concentrates, and cathodes.

Jackson said possible policy solutions could involve Washington setting a price floor for TC/RC charges, imposing a tariff on copper cathode, or blocking exports of copper concentrate.

"The current structures don't support the Kennecott smelter," said Jackson.

KENNECOTT TO STAY SHUT FOR A FEW WEEKS

Rio shut down part of Kennecott's mine operations this month after a worker died, the second death at Rio's operations this year.

Jackson, who plans to visit Utah later this week, said the company is investigating the death and that Kennecott's underground mine will remain closed for a few weeks.

"We will never be able to make mining a zero-risk business, but we should be able to make it a zero-harm business," Jackson said.

MONGOLIA NEGOTIATIONS

In Mongolia, Jackson oversees the Oyu Tolgoi copper and gold project. The country's government, which owns 34% of the project to Rio's 66%, is seeking to renegotiate what it has called the "unfair" ‌commercial terms.

Mongolia took a multibillion-dollar loan from Rio Tinto to fund its share of the mine's development. Rio also charges management fees.

Jackson, who was in Mongolia earlier this month, said Rio is open to reducing its management fees and the interest rate on the loan, but noted that the loan is unsecured and that Rio is guaranteeing the project's finances.

"There is a very real and significant risk that we are carrying as a company," said Jackson. "We have been negotiating in good faith for some while, and we are keen to get something done."

(Reporting by Ernest Scheyder; Editing by David Gregorio and Sonali Paul)

((ernest.scheyder@thomsonreuters.com; X: @ErnestScheyder; +1-469-691-7667; Reuters Messaging: ernest.scheyder.thomsonreuters.com@reuters.net))