The US military plans to send three additional combat brigades to Afghanistan by mid-summer this year, Defence Secretary Robert Gates told members of the Senate Armed Services Committee on Tuesday.
He said there is a possibility of increasing the number of US troops in Afghanistan, though it has not been finalised.
Gates, however, cautioned that sending more troops there may send out a wrong signal to Afghans, who hope to see their own security forces take the lead.
He said US' goals in Afghanistan must be "modest" and "realistic", stressing that its objective should be getting rid of the terrorists.
On Iraq, Gates said the US military is weighing options on how to withdraw troops from that country.
All the options and their respective risks are being presented to President Barack Obama, who will meet the Joint Chiefs of Staff at the Pentagon on Wednesday to discuss the issue, he added.
Gates is the only former Bush administration cabinet official retained by Obama.