The planned launch of an Atlas V carrying the New Horizons spacecraft "has been delayed for at least one more day," the space agency said in a statement.
It was delayed because of a major power outage in the region around Laurel, Maryland.
The area is home to the Johns Hopkins University's Applied Physics Laboratory, which operates the spacecraft and manages the mission.
"The launch is scrubbed for 24 hours," the statement said.
It had also been cancelled on Tuesday because high winds at the launch site at Cape Canaveral, Florida put the liftoff at risk.
The mission aims to send a spacecraft the size of a grand piano and packed with scientific instruments to Pluto, the last of the nine official planets in our solar system.
Long trip
It will take the craft at least 10 years to reach the planet, traveling at unparalleled speeds of up to 75,000 kilometers an hour.
If NASA fails to launch the probe by January 27, the trip will take several more years.
NASA is trying to take advantage of a unique planetary alignment that puts Pluto, in a position that would let the spacecraft, carrying the probe, use Jupiter’s gravitational force as a sling shot, accelerating its speed to cut off about 30 months from the trip.
The craft is scheduled to approach Pluto, which has a lopsided, non-circular 248-year orbit around the sun, between July 2015 and July 2017.
Once it arrives, the probe will take an estimated four hours and 25 minutes for its radio-transmitted data to reach Earth.
Scientists say the mission must be carried out before 2020 because, after that date, Pluto will be too far from the sun and its atmosphere will be frozen.
The distant Pluto is the only known planet that has not been explored by a space probe.
It remains a mystery 75 years after its discovery.
"What we know about Pluto today could fit on the back of a postage stamp," said Colleen Hartman, deputy associate administrator for NASA.
Onward journey
The craft will explore Pluto and its largest moon Charon before continuing on a trajectory away from the sun.
It will then spend five more years probing the icy and rocky bodies of the Kuiper Belt, which some astronomers believe Pluto is part of.
Scientists hope the ambitious journey will help them better understand the origins of Earth and the other planets some 4.5 billion years ago.