But North Korea has yet to announce its plans, leaving some uncertainty whether and when it will proceed with a launch that would be sure to draw international condemnation.
The U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies said Thursday the recent activity at the Sohae site on North Korea's northwest coast suggests it could be ready to launch a three-stage rocket by the end of the first week in December.
A commercial satellite photo taken Monday shows two long trailers, likely used to carry the first two stages of a rocket, according to an analysis written for 38 North, the institute's website. The trailers are parked near the main missile assembly building, where it says rocket stages would be checked before moving to the launch pad for takeoff about a half-mile away.
In April, North Korea fired a rocket from the same site in a failed attempt to launch a satellite into space, drawing U.N. censure as that technology can be easily converted into use for missiles. The launch dashed prospects for a resumption of international aid-for-disarmament talks.
South Korean officials confirmed Thursday there are signs of preparations at the rocket site. A launch in the next few weeks would be seen in Seoul as timed for South Korea's Dec. 19 presidential election.
Victor Cha, a former White House director of Asia policy, said Pyongyang has a track record of reacting to elections in both the U.S. and South Korea in provocative ways, most recently when President Barack Obama took office in 2009. North conducted a rocket and nuclear test within four months.
Another motivating factor for the North could be that South Korea recently won U.S. approval to expand its ballistic-missile range, and this week, was readying its own satellite launch. However, it scrapped those launch plans Thursday, citing technical problems.
North Korea conducted nuclear tests in 2006 and 2009, and Washington says Pyongyang uses long-range rocket launches to develop missiles that could target the United States, although it is not yet believed to have miniaturized a nuclear device to mount on a missile.
A rocket launch would not only dismay the U.S. and its allies, but the North's chief ally and source of economic support, China, which is midway through a leadership transition.
"If North Korea does carry out a launch, Beijing will not be happy," said Evans Revere, a former senior U.S. State Department official and expert on East Asia. "It flies in the face of China's request for North Korea to reduce tensions in the region and not escalate them."
Past launches have happened in spring or summer when weather conditions are better, but according to the analysis on the institute's website 38 North, there are several telltale signs that one is being readied now.
As well as the trailers, the images show empty tanks in four locations suggest fueling preparations. There's work under way at an instrumentation site that would monitor a launch. Also, temporary structures for keeping the snow off cars have been erected near a building used to house visiting VIPs.
But any launch could still be weeks away. The analysis notes that North Korea has yet to provide notification for international flight and shipping of splashdown zones for the used rocket stages, as it did before the April launch. Nor has it filed a plan for a frequency for a signal that would be emitted by a satellite.
David Wright, a physicist with the Union of Concerned Scientists, said the launch preparation so soon after the April failure "calls into question whether the North could have analyzed and fixed whatever went wrong." North Korea has yet to successfully test a rocket with a range of more than 800 miles.
Another failure would embarrass young North Korean leader Kim Jong Un, not yet a year in the job after the death of longtime ruler Kim Jong Il, his father.
Associated Press writers Foster Klug and Sam Kim in Seoul, Seoul Korea, contributed to this report.