By Hilary Russ

NEW YORK (Reuters) - Amtrak said on Tuesday that it would cancel three round-trip trains every weekday between New York and Washington, D.C., when it starts major repairs this summer at New York's Pennsylvania Station.

In what New York Governor Andrew Cuomo dubbed the "summer of agony," major disruptions are expected for riders as Amtrak replaces switches and rails in New York's Penn Station. Amtrak owns the rails and station and leases them to commuter lines operated by NJ Transit and the Long Island Rail Road.

The work was originally scheduled to take years but was expedited after recent derailments and other problems that left hundreds of thousands of commuters delayed for hours because of decaying infrastructure.

Amtrak President Wick Moorman said in Tuesday's statement that its "own service at Penn Station will face the largest impact of the three railroads in terms of proportional reductions in train service during the work period."

Amtrak's routes between New York and Boston, as well as Acela trains, are not expected to change, the national passenger rail company said in Tuesday's statement.

New York is a major choke point on the railroad's Northeast Corridor, its most lucrative route, between Boston and Washington. About 140 Amtrak trains use Penn Station daily.

The busiest rail hub in the nation, Penn Station is a web of more than 20 tracks, the most complicated section of which will see significant work between July 10 and Sept. 1.

Some Manhattan companies are exploring alternate work plans for employees so they can avoid the mess altogether.

Amtrak and NJ Transit officials are scheduled to testify on Wednesday before a New Jersey legislative committee. Riders are fuming because NJ Transit's popular Morris & Essex Midtown Direct line will be diverted during the repair program to Hoboken, where ferries and alternate train lines connect to Manhattan.

"We need to thoroughly examine the agreement that NJ Transit, Amtrak and the Long Island Rail Road reached and ensure that the pain is equally shared among commuters on the three railroads," state Senator Bob Gordon said in a statement.

(Reporting by Hilary Russ; Additional reporting by David Shepardson in Washington; Editing by Daniel Bases and Lisa Shumaker)