U.S. Treasury says hitting debt ceiling on Monday

WASHINGTON, Dec 31 (Reuters) - The U.S. Treasury said it would hit a legal limit on borrowing on Monday but was launching new measures to keep the nation from defaulting on its debt.

A Treasury official said the federal government was hitting its $16.4 trillion ceiling on borrowing.

Separately, Treasury Secretary Timothy Geithner said in a letter to congressional leaders that the government would suspend some investments in pension and health benefit funds for federal workers beginning on Monday to free up borrowing authority.

The suspension of the investments is part of a series of measures announced last week to keep the country from defaulting on its debt.