The United States plans to send 1,400 additional combat Marines to Afghanistan to try to hold on to recent but fragile security gains, only months before a planned U.S. drawdown, The Wall Street Journal reported Thursday.

Violence is at its worst in Afghanistan with record casualties on all sides of the conflict and with the insurgency spreading out of traditional strongholds in the south and east into once-peaceful areas in the north and west.

A review by President Barack Obama last month found U.S. and NATO forces were making headway against the Taliban and al Qaeda but serious challenges remained. It said the Taliban's momentum had been arrested in much of Afghanistan and reversed in some areas.

The review also said the United States was on track to begin a gradual withdrawal of its troops -- now numbering about 100,000 in a total foreign force of 150,000 -- from July 2011.

"The Marine battalion could start arriving on the ground as early as mid-January. The forces would mostly be deployed in the south, around Kandahar, where the U.S. has concentrated troops over the past several months," The Wall Street Journal said, citing unnamed officials.

NATO and U.S. officials in Kabul were not immediately available for comment on the report.

A boost in combat troop numbers, even if only temporary, could face opposition with members of Obama's Democratic Party, the majority of whom are keen to see troops start coming home.

The move could also encourage Republican rivals like Senator John McCain, who has argued against a 2011 drawdown date, saying it has only emboldened the militants.

Under pressure to show sustainable results in the first half of 2011, the temporary boost in troop numbers could help counter any "spring offensive" by Taliban militants returning from Pakistan after the cold winter months, the report said.

While fighting between insurgents and foreign troops has tended to intensify during warmer months, military commanders on the ground now speak less in terms of fighting "seasons" as both sides have stepped up their attacks throughout the year.

Last year was the deadliest of the war with a record 711 foreign troops killed, according to monitoring website Forty-one troops were killed in December alone, more than in March or April when temperatures are higher.

Afghan security forces have been hit even harder than foreign troops. A total of 1,292 Afghan police, 821 Afghan soldiers and 5,225 insurgents were killed in 2010, according to the Afghan government.

But Afghan civilians have borne the brunt of the war. The United Nations has said 2,412 civilians were killed and 3,803 wounded between January and October last year -- up 20 percent from 2009.

(Reporting by Mohammad Zargham; Additional reporting by Jonathon Burch in KABUL; Editing by Nick Macfie)

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