US copper imports rose to a two-year high in March, ending the first two months of the month's downward trend, as demand for metals increased as manufacturing continued to recover.

Copper imports have broken through high levels, but aluminum imports have fallen by 20% in the first quarter, and this trend may continue in the coming months as production restarts and high prices on the London Metal Exchange (LME) inhibit consumer buying.

According to data released by the US International Trade Commission last week, the United States jumped to 66,166 tons of imported copper in March, an increase of more than 30% from the 50,494 tons in February.

Copper imports in March reached the highest level since March 2009, when copper imports in March were 79,975 tons.

The total amount of aluminum imports in the first quarter was 311,062 tons, 20% lower than the record high of 389,539 tons hit in the same period last year.

In the United States, manufacturing growth in April was faster than expected, boosted by the increase in exports and the need to replenish inventory.

According to The Institute for Supply Management, the US manufacturing index fell to 60.4 in April, compared to 61.2 last month, slightly higher than economists' estimates.

The recovery in the manufacturing sector, which is at the core of the economic recovery in the United States, offsets the negative impact of the long-term downturn in housing and construction. The housing and construction industry is the main end-user market, accounting for almost half of the U.S. consumption.

Sterling Smith, an analyst at Country Hedging in Minnesota, said: "Manufacturing is steadily moving forward, but the property market is still in a slump."

Analysts said that in 2011, more and more aluminum in the United States will be put into production, so the demand for aluminum imports will continue to be weak.

Alcoa said in January that it plans to restart three idle aluminum smelters. In 2011, it will increase aluminum production by 137,000 tons, followed by a year-on-year increase of 200,000 tons. Alcoa is the largest aluminium producer in the United States.

Jorge Vazquez, an analyst at Harbor Intelligence, said that the restart of aluminum smelters and the surge in aluminum prices should make aluminum imports in the doldrums in the future.

It also said: "America's aluminum production in the first quarter was much higher than in previous years due to the restart of the smelter."

In addition, the three-year high of LME's benchmark aluminum prices in the first quarter was also the reason for the weak demand.

“Consumers throughout the supply chain are trying to postpone aluminum purchases, especially in January and February, given the price... This also explains the reason for the reduction in imports.”