ZAGREB, Croatia - A senior U.S. Defense Ministry official on Tuesday described Croatia as a "valued partner" in the war on terror.

Mira Ricardel, deputy assistant secretary of defense for Eurasia, visited Croatia to sign an agreement on cooperation in preventing proliferation of weapons of mass destruction. Croatia aspires to join NATO (news - web sites).

The agreement signed Tuesday by Ricardel and Croatia's Defense Minister, Zeljka Antunovic, was the first tangible sign that the Croatian pro-Western government is siding with the United States in its war on terror.

The deal, which still has to be ratified by the U.S. Congress and the Croatian parliament, would provide Croatia with knowledge and equipment needed to fight the spread of weapons of mass destruction, Antunovic said.

The agreement was not linked to the possible war in Iraq, she said, adding it covered a period of seven years. She offered no other details.

Ricardel said the deal would deepen partnership between the two countries.

"Croatia is a valued partner of the United States, a valued partner in the war on terror," she said.

Ricardel also said Croatia was "a serious candidate" for NATO membership because "its leadership is taking very decisive and difficult steps in reforming" its armed forces.

Croatia, a nation of 4.5 million that gained independence in 1992 and ended a war with Serb rebels in 1995, is reforming its military to conform to NATO standards, hoping to become an alliance member.

The country has been a member of NATO's auxiliary program Partnership for Peace since 1997, but it is not among the front-runners for alliance