Kayani expressed grave concern over the deteriorating law and order situation in the southern port city, but said any decision to call in the army to restore peace would have to be taken by the civilian government.
It is the army's duty to serve the nation, he said.
The army is prepared to assist the civilian administration in Karachi if it is deemed necessary, Kayani told reporters on the sidelines of a function at the General Headquarters in Rawalpindi on Saturday.
He parried a question on whether the government had contacted him for calling out the army in Karachi.
The army chief contended that the situation in Karachi can be brought under control by effectively using the paramilitary Pakistan Rangers and police.
It would be wrong to undermine the ability of the Pakistan Rangers, he said.
Karachi is the "jugular vein of the country's economy and it will be a great injustice if the deteriorating law and order situation there is allowed to continue for a longer period," Kayani said.
Asked whether the army intended to intervene in Karachi by itself, Kayani said this was "impossible" as the federal and provincial governments were "hectically engaged" on the issue.
He said it was "very regrettable" that innocent people were being killed in Karachi.
A wave of ethnic and political violence in Karachi has claimed over 70 lives in the past five days.
Several policemen were among those killed as supporters of different ethnic groups and political parties fought running gun battles in parts of the city.
Punjab Chief Minister Shahbaz Sharif, a senior leader of the opposition PML-N, and key members of Karachi's business community are among those who have called for the army to be deployed to restore peace in the city.
Sharif expressed deep concern at the law and order situation in Karachi and condemned the Pakistan People's Party-led federal government for becoming a "silent spectator" as the situation in the metropolis worsened.
Asked to comment on reports that traders had demanded the deployment of the army in Karachi, Sharif said the federal government should use every option, including calling in the army, to restore peace.
However, Interior Minister Rehman Malik said the army could not be called out in Karachi because it was busy in the war against terror.
The strength of the police force in the city could be increased, he said.
He claimed the mafia in Karachi was "extremely strong" and several groups were fighting with each other to expand their areas of control in the city.
The violence in Karachi was aimed at weakening Pakistan, he claimed.
"Our enemies are bent upon weakening Karachi, the commercial hub of the country, as part of their strategy to create anarchy," he said.
