ON BOARD US MILITARY AIRCRAFT: US Defense Secretary Robert Gates said Friday he has urged NATO allies to temporarily increase force levels in Afghanistan next year to protect the 2009 presidential elections.

"I suggested that we consider a temporary further increase in troops next year in connection with the elections in Afghanistan to help the Afghans provide security," Gates told reporters.

"I just laid out a marker that I thought we should think about that going forward. We didn't really discuss it," he added.

The elections, which are supposed to be held in late 2009, will be a key test of the viability of a struggling, seven-year-old US and NATO-led effort to build a democratically elected central government in Afghanistan.

Gates' comments on the flight home from Budapest followed a two-day meeting of NATO defense ministers who agreed to step up operations against a flourishing Afghan drug trade that is fueling a Taliban insurgency.

It was held amid warnings in Washington that Afghanistan is on a downward spiral, dragged down by corruption, drugs and insurgent violence.

US commanders in Afghanistan have asked for four more combat brigades and support troops -- as many as 20,000 more troops -- to counter the insurgency.

The United States has some 33,000 troops in Afghanistan, about 13,000 of them in a 50,000-strong NATO-led International Security Assistance Force.

Gates said he was satisfied with the NATO debate on drug trafficking which gave the International Security Assistance Force the go ahead to attack drug labs and traffickers.

"It is just going to be part of regular military operations. This is not going to be a special mission," Gates said, adding that the counter-drug effort was likely to focus on the southern part of the country.