UPDATE 1-Machinists union strikes improved tentative deal with U.S. railroads

(Adds NCCC statement, more details from IAM's statement)

By Aishwarya Nair

Sept 27 (Reuters) - A union representing machinists, mechanics and maintenance personnel said on Tuesday that it has reached an improved tentative contract deal with a committee representing major U.S. freight railroads.

The agreement, that covers 4,900 members, will now be put for a vote by members, a division of International Association of Machinists and Aerospace Workers (IAM) said in a statement.

The union's members had rejected an agreement reached earlier this month with the National Carriers' Conference Committee (NCCC), which represents railroad operators including Union Pacific, Berkshire Hathaway-owned BNSF and CSX Corp, demanding better terms.

Later, President Joe Biden announced that other unions, including those representing thousands of workers, and the NCCC had reached a tentative agreement, staving off a costly strike that could have crippled U.S. supply chains.

The NCCC, separately on Tuesday, said the new tentative deal implements the recommendations of Presidential Emergency Board, which includes a 24% wage increase during the five-year period from 2020 through 2024 and five annual $1,000 lump-sum payments.

"With today's announcement, all unions in the national bargaining round have ratified or are in the process of ratifying new collective bargaining agreements," it added.

A cooling off period that expires on Dec. 9 is now in place, IAM District 19 said.

Rail parties had agreed to a cooling off period as part of a deal, a standard part of ratification process in case vote fails in order to avert any shutdown, Reuters had reported earlier this month. (Reporting by Aishwarya Nair in Bengaluru; Editing by Shailesh Kuber)