New satellite images of a North Korean rocket launch site show a mobile radar trailer and rows of what appear to be empty fuel and oxidizer tanks, evidence of ramped-up preparation for what Washington calls a cover for a long-range missile test.

An analysis of images provided Monday to The Associated Press by the U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies shows Pyongyang "has undertaken more extensive preparations for its planned April rocket launch than previously understood." The images were taken Wednesday.

Charles Vick of GlobalSecurity.org told Fox News that if reports of satellite photographs of a North Korean missile are true, it would be the first "visual confirmation" of a new, more powerful launch vehicle.

The photos appear to show a mobile radar trailer, essential for any launch, standing at the end of a new dirt road running from the entrance of the Tongchang-ri site; it has a dish antenna that's probably a radar tracking system, according to the institute's analysis. Radar tracking during a launch gives engineers crucial real-time information on the performance of the rocket's engines, guidance system and other details.

"These pictures are new and important evidence that the North's preparations for its rocket launch are progressing according to schedule," said Joel Wit, visiting fellow at the institute and editor of its website on North Korea, "38 North." The images are from Digital Globe, a commercial satellite photography company.

The South Korean newspaper Chosun Ilbo Tuesday quotes government officials saying the photos show what appears to be a long-range missile at a facility in Pyongyang.

According to Vick, such a missile could have a range of 6,2000 miles, well within the range of the continental United States.

The range of the missile, for example, set to launch from a site in northwestern North Korea later this month, he says, has a range of 4,200 miles.

North Korea states the aim of that launch is to send into orbit a civilian satellite. The U.S. says it breaks a deal it struck with North Korea to suspend that country's missile testing and suspected nuclear program.

The new, larger missile or a mock-up could reportedly get its first public showing at a military parade later this month marking the 100th anniversary of the birth date of North Korea founder Kim Il-Sung. Presiding over that event will be his grandson and new leader, Kim Jung-Il.

Missile expert Charles Vick tells Fox News it is "no surprise" to him that this new, bigger rocket might be making an "appearance" as well.

If North Korea goes ahead with its planned long-range rocket launch, Washington is likely to take the matter to the U.N. Security Council, analysts say, and could tighten its already tough sanctions.

The launch would violate both a U.N. ban and an accord the impoverished country reached with Washington on Feb. 29, under which it would freeze nuclear activities and observe a moratorium on nuclear and long-range missile tests in exchange for 240,000 metric tons of food aid.

Obama, facing re-election and accused by opposition Republicans of naivete for reaching out to North Korea, pointedly visited the heavily militarized Korean border last week during a trip to South Korea for a nuclear summit. North Korea's new leader, Kim Jong Un, previously had made the visit from the northern side.

Obama implored the North's leaders "to have the courage to pursue peace," but warned that unless they changed their ways, the country would face "more isolation." But neither he nor other administration officials have said what steps the U.S. will take should North Korea launch the missile.

The U.S. and allies including Japan and South Korea could seek to clamp down further on the North's illicit weapons trade and impose additional financial and banking restrictions that have hurt North Korea in the past.

"The U.S. is highly likely to unveil another round of sanctions to send a clear political message to North Korea," said John Park, a Northeast Asia specialist at Harvard University's Belfer Center.

Washington is urging China -- North Korea's most important ally and trading partner -- to nudge its neighbor into line, but the prospects appear slim. North Korea has promoted the launch as a sign of the nation's strength and progress as it marks the centennial of the birth of its founder, Kim Il Sung. Recent satellite imagery showed preparations under way at the launch site.

The launch also may be an effort to consolidate the authority of Kim's grandson, Kim Jong Un, who is establishing a third generation of dynastic rule.

Park said that while China is doubtlessly frustrated by the North's conduct and has made a stronger public statement than it did before the 2009 launch, its ultimate concern will be to preserve the still-fragile government of Kim Jong Un and prevent a regime collapse on its own frontier.

He also doubted that Washington would risk its own relations with China by taking a new step: penalizing Chinese companies that do business with North Korea.

Fox News' Greg Palkot and The Associated Press contributed to this report.