The Bush administration said on Monday it was keeping U.S. sanctions against Libya in place but promised to take "tangible steps" to improve relations if Tripoli follows through on its pledge to get rid of its weapons of mass destruction. "Despite the positive developments, the crisis with respect to Libya has not been fully resolved, and I have therefore determined that it is necessary to continue the national emergency declared with respect to Libya and maintain in force the comprehensive sanctions against Libya," President Bush said in a letter members of Congress issued during his visit to St. Louis. But Bush also pledged: "As Libya takes tangible steps to address those concerns, the United States will in turn take reciprocal tangible steps to recognize Libya's progress." Although Bush did not spell out what steps he would take if Libya follows through, the administration could roll back some of the sanctions later this year as a goodwill gesture, leaving others in place for leverage. U.S. officials said no decisions have been made. Bush's announcement was widely expected despite comments from Libya's prime minister suggesting his government was pressing for their quick removal. Tripoli and the families of the 1988 Lockerbie bombing victims agreed on an April deadline for ending the U.S. sanctions, although a lawyer for the families said the deadline could be extended. The United States has long maintained it is not bound by the agreement between the families and Libya and would remove its sanctions only when it deemed appropriate. Lifting the sanctions would pave the way for U.S. oil companies, including Oasis Group that includes Marathon Oil Co., ConocoPhillips and Amerada Hess to resume activities in Libya, which they had to abandon when expanded U.S. sanctions forced them to pull out in 1986. **PHOTO CAPTION*** Moamer al-Gadhafi.