MEXICO CITY, July 30 (Reuters) - Grupo Mexico, a major

copper producer, is looking to decide on investments for

projects in the United States within the next three to five

years, an executive said on a call on Wednesday, as Washington

prepares to levy tariffs on some copper products.

U.S. copper prices plunged on Wednesday after an order

signed by President Donald Trump

fell short

of the sweeping restrictions expected and left out copper

input materials such as ores, concentrates and cathodes.

Grupo Mexico had earlier said it saw the proposed

tariffs as an

opportunity to invest

some $6 billion in expanding copper projects in Arizona run

by its local subsidiary Asarco, including reopening a mothballed

smelting operation.

"Now with the recent developments, we're continuously

evaluating if we should or we should not restart our Hayden

operation," Leonardo Contreras, finance chief of Grupo Mexico's

mining division told analysts in a conference call.

"We will continue to monitor on how these global changes

happen on a daily basis," Contreras added.

The tariff was intended to promote domestic development

but the United States depends on imports for nearly half of its

refined copper needs, and homegrown projects often take years to

get off the ground.

Chile, Canada and Mexico are currently its main

suppliers, though China buys the bulk of their exports.

Grupo Mexico said that although the trade war between

the U.S. and China could affect global economic growth and

consequently demand for copper, it maintained a "very positive"

outlook for long-term copper growth in Asia.