WASHINGTON (AFP) - Defence Secretary Robert Gates is weighing a possible temporary expansion of the US army to ease the strain from wars in Afghanistan and Iraq, his press secretary said on Wednesday. Gates was discussing the idea, backed by Senator Joseph Lieberman, with senior officers to add 30,000 troops to the active-duty army, press secretary Geoff Morrell told reporters. The possible expansion from the current strength of 547,400 would be designed to get them through what is still a stressful period as we draw down in Iraq and continue to plus-up in Afghanistan, Morrell said. So he is engaged in discussions with a number of people about that possibility, he added. Any expansion would be temporary but would carry a significant price tag, possibly more than a billion dollars, army officials said. General Peter Chiarelli, the armys vice chief of staff, has told lawmakers that at any given time about 30,000 Army troops in the current force are not available to deploy to combat missions. About 10,000 army personnel are wounded and receiving medical care, another 10,000 are in training programs and the remainder have been ordered to serve the Defence Department or other agencies and cannot be pulled from their duties. Meanwhile, the Pentagon has said that US soldiers serving in the wars in Iraq and Afghanistan will still have access to cigarettes despite a report urging a tobacco-free military force. Robert Gates has no plans to ban the sale of cigarettes or chewing tobacco for troops doing combat duty, his press secretary Geoff Morrell told reporters Wednesday. He knows that the situation they are confronting is stressful enough as it is, and I dont think he is interested in adding to their stress levels by taking away one of the few outlets they may have to relieve stress, Morrell said. And that may be chewing tobacco or smoking a cigarette. The comments came after a recently released report by the Institute of Medicine (IOM) report called for adopting measures that could make the military virtually tobacco-free within 20 years. The Defence Department spent 564 million dollars in 2006 treating tobacco-related illness in the military, the report said. It found the proportion of smokers in the US armed forces is higher than in the civilian population, with around 32 percent of soldiers using tobacco products, compared to 20 percent of civilians. Military personnel on deployments were twice as likely to be smokers than their home-based counterparts, said the report, which was sponsored by the Pentagon and the Veterans Association. Morrell said Gates would carefully study the report, which cites subsidized tobacco products on military bases as a contradiction to the Pentagons stated policy to discourage smoking. Latvian lawmakers, meanwhile, on Thursday overwhelmingly rejected an opposition attempt to force the government to pull the Baltic states troops out of NATOs Afghanistan mission. Sixty-two members of the 100-seat parliament voted against a bill from the left-wing Harmony Centre movement, which demanded that Latvias 160-strong contingent be brought home by October. Twenty-three voted in favour of withdrawing from NATOs International Security Assistance Force. One abstained and the remainder did not take part. The NATO force was deployed in Afghanistan in the wake of the US-led overthrow of the Taliban in 2001. There are currently around 90,000 international troops, mainly US, British and Canadian, deployed in Afghanistan to battle a Taliban-led insurgency. Latvian soldiers are based in the northern province of Faryab, which sees little of the violence raging in the south. They have been serving in Afghanistan since February 2003, and three of their number have been killed. Harmony Centre which enjoyed a solid showing in last months municipal and European parliamentary elections is rooted in Latvias large ethnic Russian population and is traditionally wary of the centre-right governments pro-US foreign policy.