Straw used more conciliatory language towards Syria
Arab countries have joined Russia and the European Union in criticising the United States for making threats against Syria over the war in Iraq.
The US said it might impose economic, diplomatic and other unspecified sanctions against Damascus if President Bashar al-Assad failed to take what it called the right decisions.
The Secretary General of the Arab League, Amr Musa, said he was astounded by the threats and an Egyptian spokesman warned against what he called the targeting of Arab countries one by one.
Amid furious speculation about whether the US might set its sights on Syria militarily UK Foreign Secretary Jack Straw, on a visit to Central Command in Qatar, refused to back the Washington line that Syria is a "rogue state".
And Spain - another key US ally in the Iraq war - on Tuesday spoke out against any military strike on Syria.
"Syria is and will remain a friend of Spain and will not be the target of any military action," said Spanish Prime Minister Jose Maria Aznar.
Syria under scrutiny
Earlier, Russia and the European Union urged the US to show restraint in its dealings with Syria, which is accused of developing chemical weapons and helping fugitive Iraqi officials.
Syria has strongly denied the US allegations.
Former chief United Nations weapons inspector
Richard Butler on Tuesday backed US claims that Syria helped conceal Iraqi weapons of mass destruction.
Mr Butler said that while he was in office in 1997-99 he saw evidence which seemed to indicate Syrian co-operation with Iraq.
"We had reason to believe that those were containers of chemical weapons and perhaps some other weapons," he told ABC radio.
The Americans say Syria is a "terrorist state" - it is included on the US State Department's list of state sponsors of terrorism.
But Mr Straw drew back from such descriptions saying: "Syria has an opportunity to prove that it's not in that category."
In contrast to a White House charge that Mr Assad was an "untested leader", Mr Straw said Syria was run by "intelligent people who have the future interest and welfare of their country at heart".
But Mr Straw did support America's message to Syria to a certain extent, echoing US Secretary of State Colin Powell, who said there was a new situation in the Middle East following the removal of Saddam Hussein.
"We look forward to them understanding this new reality and moving forward," Mr Straw said.
The BBC's Malcolm Brabant in Qatar says the UK's strategy towards Syria appears to be based on the premise that conciliatory language will achieve more than tough talk.
The UK view is supported by Russia, which said the US statements can only aggravate the situation and complicate a post-war settlement in Iraq.
The US has faced a chorus of disapproval over its stance, with both French Foreign Minister Dominique de Villepin and the European Union's foreign policy chief, Javier Solana, urging Washington to tone down its rhetoric.
UN Secretary General Kofi Annan has already expressed concern that recent statements about Syria may further destabilise the Middle East.
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At the White House, the presidential spokesman, Ari Fleischer, repeatedly dodged the question of whether Syria might be next for US military action - intentional ambiguity clearly designed to frighten Damascus, says the BBC's Rob Watson.
And US Defence Secretary Donald Rumsfeld said Syria had carried out chemical weapons tests in the past 12 to 15 months.
Ties between the US and Syria have long been strained by US support for Israel and Syria's backing of the Lebanese group Hezbollah and radical Palestinian groups, which Washington considers "terrorist".
Israel has urged the US to put heavy pressure on Syria to oust the Palestinian militant groups from Damascus and Hezbollah guerrillas from southern Lebanon.
Syrian foreign ministry spokeswoman Bouthana Shaaban hit back, insisting that "the only country in the region which has chemical, biological and nuclear weapons is Israel".
Syria has also firmly denied that it is giving safe haven to members of Saddam Hussein's regime.
Ms Shaaban told the BBC the fact that a senior Iraqi official had been found near the Iraqi-Syrian border was "evidence that Syria didn't let him in, and didn't let any member of the family in or anybody of the regime in".
UK Prime Minister Tony Blair told Parliament he had received an assurance from Syrian Mr Assad that no fleeing Iraqi officials would be allowed into Syria.