While pleased with steps taken by Libyan leader Muammar al-Qaddafi (search) to end his programs of mass destruction, the Bush administration is not ready to reward him by lifting economic curbs or restoring diplomatic relations.

Administration officials are taking a long look at how al-Qaddafi follows through on his promise. Libya remains on the State Department's list of seven countries that sponsor terrorism.

On Tuesday, a U.S. cargo plane carrying some 55,000 pounds of nuclear and missile components arrived in Tennessee from Libya.

Also, the "most sensitive documentation" associated with Libya's nuclear program arrived by plane last week, and Libya has begun destroying chemical munitions, White House spokesman Scott McClellan said.

McClellan praised al-Qaddafi as courageous and administration officials indicated the Libyan leader eventually could expect some easing of economic pressure if he continues on a cooperative track.

But one official told The Associated Press that Libya has not proved it no longer supports terrorism. As a result, the State Department is not ready to cancel Libya's designation as a terror sponsor, said the official on condition of anonymity. Therefore, at least some economic sanctions will remain in place.

The plane carrying the components arrived at McGhee Tyson airport outside Knoxville, Tenn. The components included stock to enrich uranium, centrifuge parts and guidance sets for long-range missiles, McClellan said.

The equipment probably will be evaluated at the Oak Ridge nuclear weapons plant, the major U.S. storehouse for bomb-grade uranium.

Sen. Lamar Alexander (search), R-Tenn., called the shipment "a critical first step in securing nuclear materials and equipment to make sure they don't end up in the hands of terrorists."

Gadhafi, seeking a lifting of U.S. economic sanctions, promised Dec. 19 to end development of nuclear and all other weapons of mass destruction.

"The world can see that Col. al-Qaddafi is keeping his commitment," McClellan said. "As they take these essential steps and demonstrate its seriousness, its good faith will be returned and Libya can regain a secure and respected place among the nations."

However, the White House official said the shipments were "only the beginning of the elimination of Libya's weapons."

Rep. Tom Lantos (search), the senior Democrat on the House International Relations Committee, met Monday in Tripoli with Gadhafi for 90 minutes and reported the Libyan leader intended to follow through on his pledge.

The California congressman said he would urge the committee chairman, Rep. Henry Hyde, R-Ill., to join him in urging the Bush administration to show "good faith" in Gadhafi by ending a ban on travel to Libya.

Gadhafi's turnabout, promoted by Britain with U.S. support, is being cited by the White House as a triumph in the campaign to halt the spread of nuclear technology.

After al-Qaddafi's pledge to abandon his quest for weapons of mass destruction, Secretary of State Colin Powell (search) said, "The next step is to make sure we have a clear understanding of what Libya possesses."

Powell said the administration intended to aggressively pursue reports that Libya obtained much of its nuclear technology from Pakistan.

"We know that there have been cases where individuals in Pakistan have worked in these areas," Powell said.