CORNWALLIS, Nova Scotia (Reuters) - The Pentagon is considering a plan to send more than 20,000 troops to Afghanistan over the next 12 to 18 months to help safeguard elections and quell rising Taliban violence, officials said on Friday.

A British military vehicle drives past an Afghan man in Lashkar Gah, capital of Helmand province October 20, 2008. REUTERS/Abdul Qodus

U.S. Defense Secretary Robert Gates said he and top commanders had discussed sending five brigades to Afghanistan, including four brigades of combat ground forces as well as an aviation brigade, which a defense official said would consist mainly of support troops. An Army combat brigade has about 3,500 soldiers.

Gates said much of the infusion could take place before Afghanistan holds elections by next autumn.

“I think it’s important that we have a surge of forces before the election,” said Gates, who stressed no decision on troop deployments had been taken.

“We’ve had some very preliminary discussions,” he told reporters after meeting to discuss southern Afghanistan with his counterparts from NATO countries with troops deployed in the region.

Pentagon press secretary Geoff Morrell said more support troops, also known as “enablers,” could also head to Afghanistan as Gates considers a request by U.S. Army Gen. David McKiernan, the top commander of NATO and U.S. forces in the country.

“The commanders are looking for well north of 20,000 forces. Gates wishes to fulfill the commanders’ request,” Morrell told reporters as the U.S. defense chief returned from Cornwallis.

Violence in Afghanistan has surged to the highest levels since the 2001 U.S.-led invasion toppled the country’s Taliban government.

An Army combat brigade is already scheduled to arrive in eastern Afghanistan in January to begin training Afghan forces.

Most of the remaining forces, which could begin deploying as early as next spring, would likely head to poppy-growing southern Afghanistan where commanders say the NATO force of 18,000 troops is too small to contend with an increasingly confident Taliban insurgency.

There are now some 70,000 Western forces in Afghanistan, including 32,000 U.S. forces -- 14,500 under NATO command and 17,500 under a U.S. command.

‘SURGE’

Gates’ use of the term “surge” to describe the influx drew parallels with the 2007 U.S. force build-up that placed an extra 30,000 U.S. troops in Iraq and contributed to a sharp decline in violence there.

“The key is how do we reverse the trends of the last couple of years or so in terms of rising violence and create a better security environment in which economic and civic development can go ahead and take place,” Gates said.

“We are clearly going to be putting more troops in and I think that the prospects for being able to have these elections successfully are good,” he said.

“We all recognize the need for the Afghan government -- with our help -- to demonstrate some progress over the course of 2009,” he said.

Gates rejected speculation Afghanistan could be heading for a dire situation.

“The notion that things are out of control in Afghanistan or that we’re sliding toward a disaster I think is far too pessimistic,” he said.

U.S. President-elect Barack Obama says he wants to focus more on the Afghan war and plans to persuade other nations to send more soldiers.

But Canadian Defense Minister Peter MacKay said Obama should look to other NATO members first, rather than turning to the other seven states that took part in the Cornwallis meeting: Canada, Denmark, Britain, the Netherlands, Australia, Estonia and Romania.

“The reality is there are other NATO doors that President-elect Obama should be knocking on first,” he told the news conference. Canada has long complained that the nations with troops in southern Afghanistan are bearing a disproportionate share of the military burden.

“There is an enormous amount of goodwill that has been engendered by President-elect Obama that he might be willing to spend for a cause that he clearly believes in,” said MacKay.

Many NATO countries insist on stationing their troops in quieter parts of Afghanistan and strictly limit what kind of combat activities they can carry out.