NASA resolved lingering concerns about lines connecting the external fuel tank to Atlantis on Wednesday and moved ahead with preparations for the first space shuttle launch of the year.

Forecasters predicted a 70 percent chance the weather would be favorable for launching Atlantis at 7:38 p.m. EDT on Friday.

Engineers were concerned that measurements of two lines that connect Atlantis to its external fuel tank may not be the same as they had been at the manufacturer, which could cause a hydrogen fuel leak.

The problem was found on the tank for space shuttle Endeavour, which is having those lines replaced for a launch in August.

Engineers concluded the problem was unique to Endeavour's tank, which previously was attached to Atlantis in 2003 and then was disconnected after the Columbia disaster kept the shuttle fleet grounded for 2 1/2 years.

Leak tests on Atlantis also have shown no glitches.

"We don't have a reason to believe we have similar circumstances," said LeRoy Cain, shuttle launch integration manager.

Technicians planned to start fueling the shuttle's power cells, and the vehicle's payload doors were shut Tuesday.

"Everything is in excellent shape," said Robbie Ashley, the mission's payload manager.

Another distraction for the launch is the prospect of 569 workers at the Kennedy Space Center going on strike as early as this weekend. The workers rejected a contract offer last weekend from United Space Alliance, the space agency's primary contractor for preparing space shuttles for launch.

Few of the workers who might strike have any direct role in the final preparations for space shuttle launches, and NASA officials have said there are other employees who could fill the roles of striking workers if necessary.

"We will not be compromised as it relates to the launch, post-launch or any of the work that we do," Cain said.

The launch originally was set for mid-March but was postponed after a freak hail storm caused thousands of dings in the insulating foam on Atlantis' external tank. Technicians spent more than two months making painstaking repairs to the tank.

Hail and strong winds threatened the launch pad Wednesday afternoon as thunderstorms blew through the Kennedy Space Center.

"We would have to be so unlucky to get more hail on this tank," said launch director Mike Leinbach.

During the 11-day mission, Atlantis and its seven astronauts will deliver a new segment and a pair of energy-producing solar panels to the international space station and rotate out a crew member at the orbiting outpost.