Britain's top diplomat has taken a keen interest in Iran during his time in office, making five trips to the country to urge Tehran to yield to international demands for it to prove it is not developing nuclear weapons.
"It was a very useful and friendly meeting that covered a range of issues," the spokesman said, describing the Straw-Khatami bilateral meeting in a hotel on the fringe of the power forum being held in this Swiss ski resort.
"If you know the subjects then you would know the kind of issues I am talking about," the spokesman said, declining to give further details.
Straw also spoke to Iranian Foreign Minister Kamal Kharazi before meeting the president.
Last October, the foreign ministers of the EU's three biggest member countries -- Straw, France's Dominique de Villepin and Joschka Fischer of Germany -- visited Tehran to urge Iran to comply with International Atomic Energy Agency (IAEA) demands over its nuclear drive.
They clinched an agreement from the Islamic republic, 10 days before an IAEA deadline, that it would sign the additional protocol to the Non-Proliferation Treaty allowing snap inspections of its nuclear sites by IAEA monitors.
Speaking at a news conference at the forum earlier, Khatami strongly denied the existence of nuclear weapons in Iran.
"Iran has never had weapons of mass destruction," he declared.
"We vehemenently oppose production and manufacturing of nuclear weapons and for this reason we have extensive, sincere and honest cooperation with the IAEA," the president said.
"We have said one thing... that Iran, like other nations of the world, has the right to peaceful uses of nuclear energy."
Straw attended only the first of the five-day forum for political and business leaders in Davos, and was heading home to London on Wednesday night.