An international dragnet may have dried up some sources of money for Al Qaeda and forced it underground, but the group still has enough access to cash to carry out attacks, a top Treasury Department official says.

One reason is that the network's cost of doing business dropped when the United States forced the ruling Taliban from power in Afghanistan.

"They no longer bear the expenses of supporting the Taliban government or running (terrorist) training camps," Deputy Treasury Secretary Kenneth W. Dam told the Senate Banking subcommittee on international trade and finance.

"We have no reason to believe that Al Qaeda, however, does not have the financing it needs to conduct at least a substantial number of additional attacks," Dam said Thursday.

Dam, who coordinates strategy for the international effort to starve terrorists of money, said legislation and international agreements forged since Sept. 11 have frozen more than $112 million in terrorist-related assets. More than 160 countries have orders blocking cash to charities and other groups suspected of funding terrorist activities.

Financial institutions and political entities such as the European Union and the United Nations and also are cooperating, but some political barriers still exist, Dam added.

The Treasury Department's Operation Green Quest and the Justice Department have seized $6.8 million domestically and more than $16 million in outbound currency -- including more than $7 million in cash -- being smuggled to Middle Eastern countries, he said.

In one example, information uncovered by the military in Afghanistan led to the arrest and indictment of Jordanian-born Omar Shishani in Detroit for smuggling $12 million in forged cashier's checks into the United States. Dam later declined to comment on whether Shishani was an Al Qaeda operative.

"We believe that Al Qaeda and other terrorist organizations are suffering financially as a result of our actions," Dam told the committee. "We also believe that potential donors are being more cautious about giving money to organizations where they fear that the money might end up in the hands of terrorists."

But he said that without the burden of supporting the Taliban government in Afghanistan, the group's needs focus on the smaller task of financing future attacks.

The Wall Street Journal estimated that the Sept. 11 attacks cost Al Qaeda between $300,000 and $500,000 -- a fraction of the revenues raised by some Islamic charitable organizations which the government believes funnel money to the group.

For example, Al-Barakaat's worldwide network funneled at least $15 million to Al Qaeda annually before its assets were frozen in November, Dam said.

Some cultural and political differences create some barriers to cutting off terrorist cash. For example, the European Union differentiates between the political and military wings of Hamas and hesitates to issue a blanket order to freeze the group's assets.

"We don't recognize that difference," Dam told reporters.