AS SAYLIYA CAMP, Qatar -- British Foreign Secretary Jack Straw said on Tuesday it was up to Syria to prove it was no "rogue nation" by providing answers to charges that it took in fleeing leaders of the overthrown Iraqi government. But Straw declined to label Syria a "rogue nation" -- as Washington did on Monday -- saying: "We use different descriptions." "Syria has an opportunity to prove that it's not in that category," he told a news conference at the Qatar Central Command headquarters running the war in Iraq. "We look forward to them understanding this new reality and moving forward."

The United States ratcheted up pressure on Damascus on Monday by threatening sanctions over charges that it was harboring Iraqi leaders, developing chemical weapons and supporting terrorism, Reuters reported.

U.S. Defense Secretary Donald Rumsfeld accused Syria of carrying out tests involving chemical weapons over the past 12 to 15 months.

Syria denies it has chemical weapons or that it has ever cooperated with the administration of the now-toppled Iraqi president, Saddam Hussein.

U.S. officials stopped short of threatening to extend the Iraq war into Syria but insisted all options remain on the table. Analysts doubted Washington would launch military action, and expect it to use diplomatic pressure to try to persuade Syrian President Bashar al-Assad to change course.

"There are some important questions for Syria to deal with ... which include the question of chemical weapons," Straw said.

His cabinet colleague, Defense Secretary Geoff Hoon, would not say explicitly on Monday whether Britain believed Syria had chemical weapons, but told reporters in London he had concerns about "efforts they have made certainly in the past".

Syria has been on the U.S. list of countries supporting terrorism for many years, and some hawks in Washington say that after Iraq, the United States should set its sights on "regime change" in Syria and Iran.

Its bitter opposition to the war on neighbor Iraq has further outraged Washington, which invaded Iraq almost a month ago to topple Saddam and destroy his alleged cache of weapons of mass destruction.

But Straw sought to play down the strains with Damascus. "We in the United Kingdom have tried to improve relations with Syria. There is an agenda for Syria and it's important that they take it in a constructive way."

He denied the United States and Britain had lined up a list of countries against which they were planning military action. "There isn't a list, and Syria isn't on it," he said. "But Syria has got to understand the seriousness of this situation."