The warning has been issued after 'exceptionally high' floods developed upstream in the Indus and Chenab rivers.
According the sources, Indus was in 'very high' flood at the Chashma barrage where flows crossed 803,575 cusecs on Wednesday, Aug 11.
The 'exceptionally high flood' carrying cumulative flows in excess of 1.05 million cusecs from Taunsa and Trimmu may reach Guddu in two to three days, said officials on Aug 11.
The officials also said that flood peak at Guddu is likely to inundate low-lying areas of Khairpur, Jacobabad, Ghotki and Sukkur districts after Aug 13.
Flood destroyed a large area of Pakistan in Jul 2009.
In addition to causing major human loses, it has destroyed hundreds of thousands of homes, washed away crops and livestock.
The United Nations says that Pakistan will need billions of dollars to recover from the deluge, which is being described as the worst in the last 80 years.