WASHINGTON — The Obama administration said Saturday that it strongly opposed central elements of two Congressional efforts to enforce copyrights on the Internet, all but killing the current versions of legislation that has divided both political parties and pitted Hollywood against Silicon Valley.

The comments by the administration’s chief technology officials, posted on a White House blog Saturday, came as growing opposition to the legislation had already led sponsors of the bills to reconsider a measure that would force Internet service providers to block access to Web sites that offer or link to copyrighted material.

“Let us be clear,” the White House statement said, “online piracy is a real problem that harms the American economy, threatens jobs for significant numbers of middle class workers and hurts some of our nation’s most creative and innovative companies and entrepreneurs.”

However, it added, “We will not support legislation that reduces freedom of expression, increases cybersecurity risk or undermines the dynamic, innovative global Internet.”