May 11 (Reuters) - Russian aluminium giant Rusal posted higher first-quarter recurring net profit on Friday amid stronger aluminium prices, but warned that sanctions imposed by the United States in April could harm its business.

Washington last month imposed sanctions on Russian billionaire Oleg Deripaska and several companies in which he is a large shareholder, including Rusal, En+ and GAZ, in response to what the United States called Russia's "malign activities."

Rusal's recurring net profit rose by 22.4 percent to $531 million from $434 million for the same quarter of last year, the world's second biggest aluminium maker said.

Rusal said its current situation was largely affected by the sanctions imposed by the United States on April 6 and repeated its assessment that it is "highly likely that the impact may be materially adverse to the business".

"In present circumstances, any forecast or outlook made or previously made should be deemed unreliable and may become irrelevant due to ongoing developments on the market at this period of time," it said.

(Reporting by Melanie Burton)