Relocating a two-mile stretch of Highway 99 in west-central Fresno will be no easy feat in the proposed development of a high-speed train line through the city.

That's why the California High-Speed Rail Authority will look to the state's highway department to handle the work instead of contractors who would build the first section of the state's high-speed rail project in Fresno.

The California Department of Transportation will be responsible for moving Highway 99 between Ashlan and Clinton avenues.

"This is a state highway, and what Caltrans does best is highway work," said Lisa Marie Burcar, a spokeswoman for the authority. "They are the experts on the highway system, so it makes sense to have them do this portion of the work."

Caltrans officials acknowledged that they are working on the project but indicated that some details have yet to be firmed up.

"Caltrans is working diligently toward an interagency agreement with the High-Speed Rail Authority to identify the scope, cost and timing of the Highway 99 realignment project in Fresno," the agency said in a statement Tuesday.

A 29-mile segment of the line from east of Madera to the south end of Fresno is proposed to be the first stretch built on what would ultimately extend to a 520-mile system of trains connecting Los Angeles and San Francisco through the San Joaquin Valley.

That first construction contract, for which five teams of contractors have been invited to bid, is expected to cost between $1.5 billion and $2 billion. The authority believes construction on the section could start late this year or early next year and be completed in 2016.

All of the work, however, will depend on whether the state Legislature agrees to use $2.7 billion in high-speed rail bond money from Proposition 1A, approved by state voters in 2008.

The federal government has pledged about $3.3 billion for the first sections of construction between Madera and Bakersfield, but that money will evaporate if lawmakers decline to pony up matching money from Prop. 1A in the state's 2012-13 budget.

From the San Joaquin River through Fresno, the proposed rail route generally runs southeast along the Union Pacific Railroad freight tracks and Highway 99 through downtown. South of downtown, the line would curve southward to run along the BNSF Railway freight tracks near Cedar Avenue.

Rail authority representatives said Caltrans' expertise in road construction makes it an attractive option for the work on Highway 99.

Between Ashlan and Clinton avenues, the six-lane freeway snuggles up against a Union Pacific Railroad yard on the east side, leaving no room to shoehorn the proposed high-speed rail line into its planned route.

"We have urged that the better solution to the relocation of that highway would be to have Caltrans do that work rather than put it in the [construction] contract ..." Thomas Fellenz, the rail authority's acting CEO, told the rail authority board last week. "They will be relocating Highway 99 on our behalf, and we'll pay them for that work."

The rail authority's plans call for shoving the freeway westward by 100 feet or so -- onto property now occupied by a string of businesses. They include a pair of mini-storage companies, several motels, a mobile-home park, an RV dealership, a truck stop and an assisted-living facility.

Three off-ramps on that stretch of the southbound highway -- Dakota, Shields and Princeton avenues -- also would be displaced. It is not clear whether those ramps would be rebuilt to provide access to businesses and neighborhoods to the west of the freeway.