SANTIAGO, July 20 (Reuters) - Chile's peso has enjoyed an extended rally since the central bank last week announced a $25 billion intervention to buoy the currency after a series of historic lows, but it may face a bumpier path in the coming weeks.

At Tuesday's close, the peso finished up 1.81% at 923.80 per dollar, taking its gains to 13.21% from a historic low of 1,045.80 on Thursday, before the intervention.

On Monday, the peso was aided by a hike in the price of copper, of which Chile is the world's largest producer, but the currency continued its strong run on Tuesday even as the price of the metal fell.

"For a lot of people the question is why the (exchange rate) keeps (improving) after the intervention and fall of copper today," said Jorge Selaive, chief economist of Scotiabank Chile, adding that other internal factors are aiding the peso's ascent.

Selaive said a "brutal" drop in risk fund shares in the country's AFP pension system is leading to investment in more conservative funds, resulting in AFPs selling dollars, aiding the exchange rate.

As well, he said the central bank hasn't announced how it will "sterilize" the intervention, or remove the excess dollars it is injecting into the system through daily currency auctions, but signs point to the bank letting bonds with less than a 360-day maturity expire.

Many of those bonds were issued at lower rates before a recent string of rate hikes.

"So the effect of the lowered interest rate will concentrate in that time frame," he said.

Another contributing factor is that foreign investors are holding off on buying dollar futures contracts, he said.

"They're waiting for the exchange rate to stabilize at new levels to reevaluate their strategy in Chile," Selaive said.

A global surge in the U.S. dollar has pushed down currencies worldwide, but Chile's peso has been particularly volatile, partly due to its floating exchange rate.

That has made it more susceptible to speculation related to copper's fluctuating price and political uncertainty over a proposed new constitution, as well as the recent intervention, according to Victor Salas and other economists at the University of Santiago.

"This is going to be an unclear, unclean drop in the exchange rate," in terms of the number of pesos that a U.S. dollar can buy, Salas said, adding that the real effect will take weeks to see.

(Reporting by Fabian Cambero and Alexander Villegas; editing by Richard Pullin)