He said troops, police and volunteers had already rescued more than 12,359 people but that help from foreign governments was needed.
"We are trying our level best to provide basic necessities, but the potential for a more serious situation is there," he told a news conference. "We cannot wait for that to happen."
Teodoro said the country needed emergency supplies, generators, food and drinking water.
The United Nations said on Monday that it would help the Philippines.
Ban Ki-moon, the UN secretary general, told Alberto Romulo, the Philippine foreign affairs secretary, that the UN was considering issuing a flash appeal for emergency assistance.
John Holmes, the UN humanitarian chief, said UN Office for the Co-ordination of Humanitarian Affairs (OCHA) personnel were already assisting in relief operations in Manila and that more staff were on their way to assess the situation and the kind of assistance required.
"We are heartened by the assurances given by the Secretary General and the Undersecretary General that the United Nations will take positive action on our request for assistance,” said Romulo said.
The United Nations Children's Fund and the World Food Programme have also already provided food and other aid and the US has donated $100,000 and deployed a military helicopter and five rubber boats manned by about 20 American soldiers from the country's south, where they have been providing counterterrorism training.
The Philippine government has declared a "state of calamity" in metropolitan Manila and 25 storm-hit provinces, allowing officials to use emergency funds for relief and rescue.
|The homes of nearly two million people were affected by the floods [AFP]
The National Disaster Co-ordinating Council said on Tuesday that the homes of nearly 1.9 million people in Manila and surrounding areas were affected by the floods, with nearly 380,000 people brought to schools, churches and other evacuation centres.
Residents in the capital, Manila, 80 per cent of which was under water at one point, have been queuing to get food and other supplies.
Critics say the government's handling of the floods left much to be desired, with some saying that officials had little idea how to respond as receding waters revealed the extent of the devastation.
But Boris Joaquin, from the international charity World Vision, told Al Jazeera from Manila that the government should not be blamed.
"It's really because nobody expected something like this... I've never seen Manila flooded this much ... it's really something overwhelming," he said.
He explained that relief teams were finding it hard to gain access to affected communities but said the upside was that "there's more collaboration happening" between the government and non-government organisations.
"Everybody's putting down whatever agenda they may have just to be able to unite" to tackle the crisis, he said.