Afghanistan's ruling Taliban has been further isolated after Saudi Arabia cut relations with Kabul.
Japan has followed the US lead in moving to freeze suspected terrorist assets, and Russia and central Asian republics have offered support for potential US military action against Afghanistan.
Following Saudi Arabia's move, Pakistan is the only nation to recognise the Taliban - believed to be sheltering the mastermind behind the US terror strikes.
"The Saudi government announces that all relations with the Taliban are cut," said a statement carried by the official SPA news agency. The decision follows a similar move by the United Arab Emirates.
Japan has also moved to target terrorists' sources of funding. "We are now preparing to freeze such assets in Japan," Finance Minister Mr Masajuro Shiokawa said.
Russian President Mr Vladimir Putin said he would allow some US flights to use his country's airspace "for humanitarian missions in the regions where anti-terrorist missions are conducted".
He said Russia may also participate in search-and-rescue missions and was willing to provide military supplies to anti-Taliban forces in Afghanistan.
Turkmenistan and Kazakhstan have said they too would open their airspace to "humanitarian" flights, and Ukraine said it would allow access to some US military flights.
Officials in Uzbekistan said US surveillance planes already were deployed in the central Asian nation.
US warplanes, ships and troops are moving into staging areas close to Afghanistan in central Asia.
But in Afghanistan, the Taliban's spiritual leader, Mullah Mohammad Omar, was defiant, warning terrorism would continue as long as US troops remained in the Middle East and while it supported Israel.
AFP