The statement comes toward the end of a month that already has been the deadliest of the year.
The militant group's leadership vowed that "every possible tactic will be utilised in order to detain or inflict heavy casualties on the foreign transgressors."
In a sign of Taliban's determination to replace Afghanistan's government with one promoting a stricter interpretation of Islamic law, they named their new offensive after a legendary Muslim military commander, Khalid ibn al-Walid.
Also known as "the Drawn Sword of God", he was a companion of Islam's Prophet Muhammad.
US-backed efforts to try to reconcile the Islamic militant movement with the Afghan government have so far failed.
Insurgents intensified attacks this spring as they try to position themselves for power ahead of national elections and the planned withdrawal of most US and other foreign combat troops by the end of 2014.
April has already been the worst month for combat deaths so far this year. According to an Associated Press tally, 257 people have been killed in violence around the nation. During that time 217 insurgents have died.
Still, the top US commander in Kabul, Marine General Joseph Dunford, said on Wednesday that the security situation has improved across the country.
"As the traditional fighting season begins, the insurgency will confront a combined " Afghan force of 350 000 soldiers and police, he said.