HOUSTON, Jan 7 (Reuters) - Exxon Mobil ( XOM ) signaled

on Tuesday that sharply weaker oil refining results, asset

impairments and lower oil prices would reduce its fourth-quarter

earnings by about $1.75 billion from the prior quarter.

The oil major also said in an SEC filing that the

impairments would knock off about $600 million, mostly in the

upstream business. The company's filing did not specify a reason

for the impairments.

Exxon is expected to post a profit of $1.76 a share in

the quarter, down from $2.48 a share, in the same quarter last

year, according to financial firm LSEG.

Exxon's earnings snapshot signaled profits "well below

consensus," said Biraj Borkhataria, an oil analyst with RBC

Capital Markets, in a note to investors. The forecast showed

"significant headwinds" in refining, he added.

The company indicated oil refining margins would cut

earnings by between $300 million and $700 million from the

third-quarter level. It also signaled timing effects would lop

off another $500 million to $900 million.

U.S. refiners had profit margins squeezed last year with

weaker-than-expected demand for gasoline and diesel and greater

production across the globe.

Exxon's snapshot is closely watched for clues to how

other oil majors will fare when they begin releasing results

this month.

Oil prices declined about 6% in the quarter ended

Dec. 31 from the prior three months, and down nearly 12% from a

year-ago, as traders worried about global oil demand.

The drop was partially offset by higher U.S. prices for

natural gas, which were up about 30% from the prior quarter.

The industry bellwether had posted $8.6 billion in

earnings for the third quarter, and an adjusted profit of $9.96

billion in the year-ago fourth quarter.

The company will release final results on Jan. 31, the

filing said.