Drag the slider up in this interactive photograph to see Pakistan's Indus River as it appeared on Aug. 9, 2009. Pull the slider down to see the flooded region on Aug. 12, 2010, a year later. (NASA).

Foreign Affairs Minister Lawrence Cannon says Canada will continue to be part of the flood response in Pakistan but has no immediate plans to increase the amount of money that has been pledged.

But Cannon, who was in New York on Thursday for a special meeting of the United Nations General Assembly, did say, "We are not closing any options to further assist the people of Pakistan in their hour of need."

Canada has already pledged $33 million for flood relief efforts in Pakistan. Cannon said Canada will continue to work with the government of Pakistan and humanitarian agencies to ensure assistance reaches affected populations as quickly as possible.

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"The purpose of the meeting today  is … to focus the world community's attention on the gravity of the situation that is taking place," he said in a teleconference.

Cannon met UN Secretary General Ban Ki-moon and Pakistan Foreign Minister Shah Mahmood Qureshi to discuss the disaster.

"The first tranche of the amount of money, the $25 million, will certainly help in terms of providing shelter, nutrition, water, health," he said.

Part of Canada's contribution just arrived in Pakistan and includes 1,000 all-weather tents, 1,000 tarps and almost 4,000 mosquito nets.

The United States will provide an additional $60 million US to flood-ravaged Pakistan, bringing its total contribution to flood relief efforts to $150 million, Secretary of State Hillary Clinton says.

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Speaking at the special meeting of the General Assembly on Thursday, Clinton called the floods a "humanitarian disaster of monumental proportions," and called on other nations to help Pakistan in its time of need.

"As we meet, we fear a new wave of water may be about to sweep through areas that have already been devastated," Clinton said.

About 20 million people in Pakistan have been affected in some way by the flooding. More than 1,600 people have been killed.

Roughly four million people — double previous estimates — have been left homeless, the United Nations says.

Speaking ahead of the high-level UN meeting, Richard Holbrooke, the U.S. special representative for Pakistan and Afghanistan, said "many billions" of dollars will be needed to rebuild Pakistan after the massive floods.

Floods create a 'slow-motion tsunami'

The floods have created a "slow-motion tsunami" in Pakistan, the UN secretary general said.

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A child sits amid the ruins of his family's house in the flood-ravaged town of Adiel Khan in Pakistan's northwest Khyber-Pakhtunkhwa province on Thursday. ((Tim Wimborne/Reuters))

The UN has called for roughly $460 million to help meet immediate needs in Pakistan, but response has been slow. Ahead of Thursday's meeting, the UN said it had raised roughly half the amount needed to provide people with emergency shelter, clean water, food and medicine.

Canadian Red Cross spokesman Howard Arfin said a "health disaster" is slowly growing in the country.

"It’s not as dramatic as a tsunami wave or, more recently, the earthquake in Haiti, but the impact on people is very, very real," Arfin said from  Islamabad.

"It’s not immediate. It’s slow with the kinds of diseases that are brought on by water, that are brought on by lack of food, that are brought on by lack of shelter," he said.

The World Health Organization has said that about six million people in Pakistan are at risk from water-borne diseases.

Reporting near the town of Baseera, in Sindh province, the CBC's Adrienne Arsenault said the next seven days are critical for the area as floodwaters are still rising.

On a relief mission Thursday in a Pakistani army boat, she said water levels are so high that she was able to pluck dates from the tops of palm trees.

Many area men have refused to leave their homes, choosing to stay to protect them.

"The army keeps trying to get them to get out," she said. "They don't want to, and so [the army] ends up constantly ferrying out enough rations for a week or so.

"Help is coming … but as one man shouted at us today from that water: 'This is a horrible place,'" she said.

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Villagers crowd the flooded streets of Baseera, Pakistan, on Thursday. ((Adrienne Arsenault/CBC))

With files from The Associated Press and The Canadian Press