Pelosi's accusation came as the Trump administration barred U.S. congressional travel on government-owned or operated aircraft during the partial government shutdown, with tensions skyrocketing between the Democratic-majority House of Representatives and the Republican White House.
The White House on Thursday had blocked Pelosi from using a military plane for a congressional trip with other high-ranking Democrats to NATO headquarters in Brussels and then Afghanistan.
Pelosi's office then was prepared to fly commercially - an idea Trump himself raised - but announced Friday morning the trip was being postponed because the administration had leaked details that could endanger the trip or the troops the speaker was to visit. A White House official denied this.
"We had a report from Afghanistan ... that the president outing our trip had made the scene on the ground much more dangerous because it was just a signal to the bad actors that we're coming," Pelosi told reporters in the Capitol.
"You never give advance notice of going into a battle area. You just never do," she said. "Perhaps the president's inexperience did not have him understand that protocol. The people around him should have known that because that's very dangerous.”
A White House official, speaking earlier on condition of anonymity, denied leaking Pelosi's travel plans, adding, "When the speaker of the House and about 20 others from Capitol Hill decide to book their own commercial flights to Afghanistan, the world is going to find out."