Prime Minister Guy Verhofstadt said the latest change would make it harder for foreigners to initiate proceedings under the legislation, which permits Belgian courts to try war and human rights crimes no matter where they were committed.

Reform to the 1993 law would oblige the defendant or victim to have Belgian residency if not citizenship, he said.

Verhofstadt said he would send the bill to parliament once his Liberal party and the Socialists had reached agreement on forming a new coalition government after their victory in legislative elections last month.

"Certain people and certain organisations, pursuing their own political agenda, systematically use this law in an abusive manner," Verhofstadt told a news conference. "Modifying the law will make it impossible to abuse this law."

He was quick to reject suggestions he had bowed to U.S. pressure, saying: "It is not U.S. pressure. The reason why we have modified it...is really because we want to keep the law."

US embassy officials could not be reached for comment.

Tensions between Belgium and the United States have risen in recent weeks, with US Defence Secretary Donald Rumsfeld, himself the target of a lawsuit, vowing to freeze spending on NATO's new headquarters in Brussels unless the law were revoked.

Ever since Belgium convicted two Rwandan nuns on genocide charges in the first trial to apply the law in 2001, it has been flooded with lawsuits against world leaders.

One high profile case was against Israeli leader Ariel Sharon, filed by survivors of a 1982 massacre of Palestinian refugees in Lebanon by Lebanese Christian militiamen. The case has been suspended given Sharon's immunity.

Belgium tried to discourage so-called "propaganda" cases by reforming the law earlier this year. It made it possible to send a case to a defendant's country if that country were democratic with a legal system that could handle it properly.

But it failed to stop more lawsuits from being filed, worsening the country's diplomatic headache.

The latest batch -- including a single-page letter sent by a Munich resident -- accuses Bush and British Prime Minister Tony Blair of war crimes in the Iraq war.

The need to reform the law was given fresh impetus last week when a local opposition party sued Belgian Foreign Minister Louis Michel for approving arms shipments to Nepal.