This Washington Post editorial sums it up rather nicely.
HOUSE SPEAKER Nancy Pelosi (D-Calif.) offered an excellent demonstration yesterday of why members of Congress should not attempt to supplant the secretary of state when traveling abroad. After a meeting with Syrian dictator Bashar al-Assad in Damascus, Ms. Pelosi announced that she had delivered a message from Israeli Prime Minister Ehud Olmert that “Israel was ready to engage in peace talks” with Syria. What’s more, she added, Mr. Assad was ready to “resume the peace process” as well. Having announced this seeming diplomatic breakthrough, Ms. Pelosi suggested that her Kissingerian shuttle diplomacy was just getting started. “We expressed our interest in using our good offices in promoting peace between Israel and Syria,” she said.
Only one problem: The Israeli prime minister entrusted Ms. Pelosi with no such message.
Not since Ted Kennedy conspired with the Soviet Union to subvert American foreign policy has a member of Congress engaged one of our enemies to undermine our position in the world.