Apple Store employees cheer during the grand opening of an Apple Store in Jiefangbei, Yuzhong District on January 31, 2015 in Chongqing, Sichuan province of China.

The overseas cash stash for U.S. companies continues to swell, with only scant hope of it being brought back home as Washington continues to debate repatriation.

American companies are holding $2.5 trillion abroad, an increase of nearly 20 percent over the past two years, according to the latest calculations from forecaster Capital Economics. The total is equivalent to nearly 14 percent of total U.S. gross domestic product.

Though the money pile could give a nice boost to the slow-growth domestic economy, corporate heads have been locked in a battle with the government over bringing the money home. The U.S. has the world's highest corporate tax rate at 35 percent, and under current law any cash brought home would be taxed at that rate.

A number of high-profile companies have come under fire for "inversions" — deals where a U.S. company buys a firm in a lower-tax nation and switches its domicile to escape high U.S. levies.

"The substantial tax bill most firms would face if they attempted to bring this cash home, however, means that it is still very unlikely to ever be repatriated under the current system," Capital Economics U.S. economist Andrew Hunter said in a note to clients. "This vast pile of foreign cash could provide a substantial boost to GDP if it was ever brought home."

At a sector level, tech and pharmaceutical companies are sitting on the lion's share of the overseas cash.

Microsoft and General Electric have more than $100 billion each abroad, while Apple is holding $91.5 billion and Pfizer has close to $80 billion. The companies did not respond to requests for comment.