Two states have gone to federal court in an attempt to block the Carter administration's plan for slashing Amtrak's national rail passenger network.

Unless either house of Congress acts by midnight to veto the administration proposal-a development that congressional leaders said yesterday was all but impossible-Amtrak is due to eliminate service over 43 percent of its routes as of Oct. 1.

But Texas Attorney General Mark White and California's Department of Transportation have filed lawsuits seeking o halt the rail system restructuring.

At the same time, Amtrak's business is continuing to balloon to record proportions, as travelers worried about the availability of gasoline for their cars are overloading the passenger system's telephone reservation networks.

Last week, a record number of callers tried to reached Amtrak; of 2 million calls placed, 1.5 million could bot be answered because of busy signals. Advance reservations now are 50 percent higher than at this time last year.

After studying these figures, as well as passenger ridership data for a number of trains now scheduled to be halted at the end of September, a growing number of representatives and senators also have begun to have second doubts about the Carter proposal.

Congressional staff members said yesterday that a major effort is being prepared to dump the Carter proposal later on the Senate and House floors-simply by introduction of amendments to Amtrak authorization bills, requiring that all current trains be continued until the impact on passenger ridership of the current energy crisis can be assessed.

An aide to Rep. Albert Gore (D-Tenn.) conceded yesterday that keeping all trains appears to be a "long shot," but several Capitol Hill staff members said they anticipate broad support for keeping many trains now slated for abandonment.

Texas Attorney General White argued, in a suit filed in U.S. District Court in Laredo, that some routes are to be dropped without providing adequate public comment. He also charged that the "history of Amtrak service in Texasis plagued with charges of inadequate and inefficient service . . . specifically Texas service has long been marred by inferior equipment, late trains, ridiculously low speeds, lack of facilities, circuitous routes, and most importantly, lack of facilities, circuitous routes, and most importantly, lack of cooperation by Amtrak executives and personnel."

U.S. DOT officials declined to comment on the suits until they are reviewed and an Amtrak spokesman expressed surprise that his firm was named in the suits, since DOT prepared the cutback plan.

Both the Texas and California suits charge that the U.S. Department of Transportation failed to provide an environmental impact statement in drawing up the Amtrak cutbacks-the same type of statements that government requires of coporations. DOT filed only a "negative declaration," contending the absence of any environmental impact.

But Susan Brown, a spokeswoman for the California DOT (Caltrans) said yesterday the federal DOT did not address such issues as increased energy consumption for auto travel, diversion of business, air pollution, employment losses, adverse impact on small business or any other environmental-related issue.

In addition, Caltrans charged in its suit that the Carter plan violates the Clean Air Act and the National Historic Preservation Act (22 railroad stations involved in the plan are historic buildings). Nor did the federal government comply with a congressional mandate to study the absence of alternative transportation in some communities affected, according to the suit, filed in U.S. District Court, in Sacramento.

Finally, the California suit alleges that a Constitutional issue is involved-the "right to travel," which would be eliminated for some people." CAPTION: Illustration, Amtrak