KABUL/WASHINGTON (AFP) - International troop levels in Afghanistan must be boosted significantly to make headway against a Taliban insurgency that has gained momentum, a team of visiting US senators said Tuesday. The US military was looking at freeing up more troops for combat in Afghanistan as President Barack Obama warned there would be no quick victory in the war. The senators, headed by Republican John McCain, visited Kabul as the Taliban carried out a deadly suicide attack in the capital and fired several rockets in a surge in violence two days ahead of elections. The senators met some of the thousands of US Marines newly deployed in the southern province of Helmand, an opium-producing Taliban bastion where rebel influence will likely prevent voting in several districts. It is very clear to me that more resources are needed in the form of additional troops as well as material, economic and other support, McCain told reporters in Kabul. I am confident that within a year to 18 months, if we give the right resources and employ the right strategy, we can see significant success here, he said. The senators met the commander of around 100,000 US and Nato forces in Afghanistan, US General Stanley McChrystal, but saw no candidates in Thursdays elections to avoid claims of favouritism. Democrat Senator Joe Lieberman said: In some senses, looking at the battlefield nationally, the momentum is slightly in the direction of the Taliban. That is what we have heard. We learned a lot from a tough fight in Iraq and while Afghanistan is clearly different, one thing we learned is that numbers matter, numbers of military personnel, numbers of civilian personnel, he said. Meanwhile, with Afghans heading into crucial elections, US defence officials in Washington said Gen McChrystal was weighing cutting back desk jobs and other support staff to free up more soldiers for combat. The idea is use troops more effectively, a US official, who spoke on condition of anonymity, told AFP on Monday. Reducing non-combat positions would mean doing more with what youve got versus asking for more troops, the official said. As campaigning ended in Afghanistan, US Secretary of State Hillary Clinton said Washington would remain impartial in the election and would work with whomever voters pick. Like the Afghan people we want to see credible, secure and inclusive elections that all will judge legitimate, she said. We look forward to working with whomever the Afghan people select as their leaders for the next five years, she added.