The United States has announced additional aid for flood relief work in Pakistan and launched a campaign, through short message service, asking its citizens to donate generously for this humanitarian cause as President Barack Obama [Images] believes US' commitment to Islamabad [Images] is far beyond fighting extremism.

"The (US) President recognises the importance of allies helping allies in times of need. Our relationship with Pakistan goes far beyond our shared commitment to fight extremists," National Security Council spokesman Mike Hammer said in a statement.

"The US government stands ready to continue to assist Pakistani authorities address the difficult challenges posed by this natural disaster," he said, adding President Obama is being kept fully informed on the evolving situation and the potential impact to well over one million Pakistani citizens.

"The US government was immediately in contact with the Government of Pakistan to coordinate our support of their response effort and to ensure aid reaches those who need it most as quickly as possible," he said.

Giving an update on the US assistance to Pakistan for flood relief work, State Department spokesman P J Crowley, said in the last 24 hours the US has sent 13 separate supply flight delivering more than 316,000 halal meals to Pakistan with another 110,000 expected to be delivered overnight.

US Defence Secretary Robert Gates has authorised the deployment of four Chinook and two Blackhawk helicopters from 101st Airborne in Afghanistan over to Pakistan to assist.

"Unfortunately, due to the weather conditions, they have not yet been able to arrive in Pakistan, but will be trying again overnight," he said.

The State Department has reactivated its texting programme, anyone can text Swat to 50555 and make a $ 10 contribution to the victims of the flooding in Pakistan.

Every text results in a donation of $ 10 to the UNHCR Pakistan Flood Relief Effort, which is providing tents and emergency aid to displaced families.

USAID has deployed humanitarian relief experts to Pakistan to work in support of the government of Pakistan and manage the overall US response effort.

The government of Pakistan has issued a detailed request for assistance which US and international officials are working to support, said a fact sheet issued by the State Department.

The US made an initial pledge of $ 10 million for humanitarian assistance under the supervision of Pakistans National Disaster Relief Authority.

US helicopters have airlifted 733 people to safety and transported 11,873 pounds of provisions to flood victims since July 30.

Four Zodiac inflatable rescue boats with power motors and two water filtration units - which provide pumping, purification, and distribution of potable water for up to 10,000 persons daily -- are being provided for use in the affected area, the State Department said.

Further, 12 pre-fabricated steel bridges have been made available as temporary replacements for highway bridges damaged by flooding in Peshawar and Kurram Agency.