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By Kerstin Gehmlich

BERLIN, Oct 7 (Reuters) - Chancellor Angela Merkel's cabinet agreed on Tuesday to extend Germany's participation in a NATO mission in Afghanistan and raise the number of troops it can send there by 1,000, sparking a heated parliamentary debate.

Berlin has been facing pressure from allies to boost troop numbers and shift soldiers to the more dangerous south to help fight Taliban insurgents. But the peacekeeping mission is deeply unpopular with voters and has bred division on the political left ahead of a general election next year.

Under a current parliamentary mandate, Germany can send up to 3,500 soldiers to Afghanistan as part of the NATO force, which currently numbers just over 50,000. Of 976 military deaths among NATO and U.S.-led forces, Germany has lost 28 soldiers.

Merkel's conservatives (CDU/CSU) and their centre-left Social Democrat (SPD) coalition partners agreed at a cabinet meeting to seek a new mandate that would allow Berlin to send a total of 4,500 troops.

"The extension of (NATO's) ISAF mission does not mean we say 'Let's continue as before'," German Foreign Minister Frank-Walter Steinmeier told parliament.

"(The new mandate) is fitted to next year's needs: More soldiers, a focus on the training of Afghan soldiers and police, more spending on civilian reconstruction. Because we want the people in Afghanistan to feel, see and live the progress."

Steinmeier, the SPD's newly named candidate to challenge Merkel in next year's election, faces a first test in the Afghanistan vote, as he needs to rally the political left around the unpopular mandate.

Germany has expanded its role in overseas missions over the last decade, but the deployment to Afghanistan is unpopular with some on the left wing of the SPD and many voters who remain uneasy about the emergence of a strong army.

Monika Knoche from the far-left Left Party said the German government was bowing to U.S. interests over Afghanistan.

"We need an exit strategy for Afghanistan. And a first step would be a withdrawal of the German army," she told parliament. "More military means more insecurity and more violence. Afghanistan urgently needs a peace process."

Kerstin Mueller from the Greens said Germany had to focus its Afghanistan strategy on civilian efforts.

"Instead of more soldiers, civilian reconstruction must be the priority," Mueller said. "It's not enough to slightly increase civilian reconstruction aid. We need a massive rise."

The Bundestag lower house of parliament is set to vote on the troop increase later this month. The new mandate is set to be valid for 14 months.

In what some saw as a bow to left-wing politicians critical of Germany's Afghanistan strategy, Steinmeier has said Berlin should no longer make troops from elite special forces available to support a separate U.S.-led counterterrorism mission there.

The defence ministry confirmed on Monday the government would not renew the KSK special forces' participation in the operation against Afghanistan's Taliban, which the United States launched after the attacks of Sept. 11, 2001. (Reporting by Kerstin Gehmlich; Editing by Kevin Liffey)

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