Afghanistan and India have signed a strategic partnership agreement.
The agreement was signed on the first day of a visit to India by Afghan President Hamid Karzai.
Indian Prime Minister Manmohan Singh said violence in Afghanistan was undermining security in South Asia.
He also said that India would stand by Afghanistan when foreign troops withdraw from the country in 2014.
The pact is believed to include a commitment by India to increase its training of Afghan security forces, including the police.
Mr Karzai's visit follows a series of attacks which have damaged ties between Kabul and Pakistan.
The BBC reports the increasingly close relationship between Kabul and Delhi will be viewed with some suspicion by Pakistan, which regards Afghanistan as its backyard.
India, a major player in Afghanistan, has already pledged $US2 billion in assistance.