By Paul Rincon
BBC News science reporter
The US space agency, Nasa, has delayed the launch of its New Horizons mission to Pluto until Thursday, after a power cut at the lab managing the mission.
The lift-off from Cape Canaveral in Florida was originally scheduled for Tuesday, but high winds forced Nasa to scrub that attempt.
Now, a storm in Maryland has caused a power cut at the spacecraft operations centre based there.
Pluto is the only remaining planet that has never been visited by a spacecraft.
The laboratory in Maryland is supposed to take control of the spacecraft 47 minutes after launch, following separation of the Atlas 5 rocket's third stage.
"Severe storms in the Baltimore and Washington area have knocked out power in several locations, including the campus of Johns Hopkins Applied Physics Laboratory," Johns Hopkins said in a statement.
"With primary power out, the New Horizons mission operations centre was on back-up power, but the... mission managers wanted to make sure they had sufficient back-up to those systems before conducting critical launch and early flight operations."
Nasa will now try for a window between 1808 GMT and 2007 GMT on Thursday to launch the spacecraft from Cape Canaveral Air Force Station.
The agency has until 14 February to launch the probe. If it fails to lift off before 3 February, up to five years could be added on to the flight time to Pluto - increasing the chances of a mission failure.
The $700m probe will gather information on Pluto and its moons before - it is hoped - pressing on to explore other objects in the outer Solar System.
The agency's administrator Dr Mike Griffin commented: "With this mission, we set out on the initial reconnaissance of the last planet known to exist in the Solar System at the time we started the space age.
"We've since discovered other large objects out there and there's some argument over whether Pluto is really a planet at all, and if it is, is it the last planet?"
Some astronomers say Pluto is not a true planet at all, and should be classed instead alongside the small, icy objects which make up the region of space known as the Kuiper Belt.
Some astronomers believe Pluto is not a true planet
This region, which lies beyond Neptune, consists of perhaps tens of thousands of icy objects spread out between 30 and 50 times the distance between the Earth and the Sun.
Pluto is thought by some to form a "double planet" with its companion Charon.
If Nasa launches New Horizons before 3 February, the probe will be in position to swing by Jupiter, using the planet's gravity to pick up speed in a slingshot manoeuvre.
This will boost the probe's speed away from the Sun by nearly 4km/s, slashing the flight time to Pluto - and reducing the chances of a mission failure.
That boost will allow New Horizons to reach Pluto in July 2015. Otherwise, the journey will take until 2018 at the earliest.
New Horizons could get to Pluto by the year 2015
New Horizons will fly by Pluto and its largest moon Charon on the same day. The spacecraft's seven instruments will carry out detailed mapping of Pluto's surface features, composition and atmosphere.
After the Pluto encounter, it is up to Nasa to decide whether to grant the spacecraft an extended mission. Should this happen, mission scientists plan to send New Horizons to visit two Kuiper Belt Objects (KBOs) with diameters of 50km (30 miles) or more.
Scientists believe they can learn about the evolution of the Solar System by studying the Kuiper Belt since it possesses debris left over form its formation.
Anti-nuclear activists have staged small protests about the spacecraft's 33kg payload of plutonium fuel.
Nasa said there was a 1 in 350 chance of a mishap that released plutonium around the launch site. Even so, it said, the chance of dangerous radiation exposure to workers and the public was low.