TORONTO - Ottawa must give Canadians more time to aid in Pakistan flood-relief efforts by extending its pledge to match donations dollar-for-dollar, doctors headed to the region said Tuesday.

Canadians have been slow to respond with donations for the Pakistan flooding compared to other disasters like the Haiti earthquake, and the deadline for the dollar matching commitment is Sunday.

The doctors, joined by Liberal MP Jim Karygiannis, called on Ottawa to extend it to the end of the month.

A fund for medical supplies set up by the doctors and the North American Muslim Foundation has raised about $3 million.

That amount lags far behind the outpouring of more than $100 million Canadians donated for victims of the Haiti earthquake. The federal government also matched those donations.

Muslims are busy fasting during the holy month of Ramadan and may not yet be in the mindset to help until the month ends on Sept. 10, Karygiannis said.

Dr. Shahnaz Dar and Dr. Muzna Ahmad were to leave Tuesday night to join two other Canadian doctors currently on the ground in the flood-stricken country.

Exhausted Pakistani doctors are treating up to 200 patients a day, said Dar, who added that's four times the number of patients she treats at her practice in Toronto.

"That's a lot of people in one day. I know I see 50 people here and by the end of the day I'm tired," she said.

Farooq Khan, the foundation's executive director, said he thinks Canadians are slower to respond to this crisis over the Haitian earthquake because they don't realize the extent of the suffering in Pakistan.

He returned from Pakistan two weeks ago and will be among another group of Canadians leaving on the weekend.

"The level of destruction that I observed and I witnessed far exceeds what I saw during the tsunami, for example, or the (Pakistan) earthquake of 2005 or the Haiti earthquake, and I have been in all these situations," he said.

Canadians should put aside any political feelings they have towards Pakistan's government, and instead think of the regular people who are dying or who have lost everything, Khan added.

"This is not an Islamic tragedy, this is not a Muslim tragedy this is not a Pakistan tragedy. It's a human tragedy," he said.

"These are human beings, so I would urge and request all Canadians to please come forward and do their share."

In a January photo-op, Harper walked into the Red Cross to make a personal donation for Haiti earthquake victims, and Karygiannis said a similar donation for Pakistan would trigger money from the Canadian public.

Some 1,700 people have died in the floods, but Khan said the devastation from the floods will linger for months, with crops being wiped out and causing food shortages and high inflation.

The need for medical treatment is high, with the most recent numbers from the United Nations showing that half a million people have respiratory infections, and thousands more have malaria or acute diarrhea.

Tests have shown cholera is in the water supply.

The United Nations says it has not yet received enough money to provide assistance to the 21 million Pakistanis affected. It brought in Hollywood actress Angelina Jolie on Tuesday to draw attention to the situation.

A second group of doctors will leave on the weekend and bring along supplies like baby formula, canned vegetables, and vitamins.

Dar says she and the other Canadian doctors are paying up to $20,000 out of their own pockets to travel.

Her daughter and husband are also accompanying her to shoot a documentary and to blog about the team's efforts.