KABUL, Afghanistan — President Hamid Karzai of Afghanistan has broadened a top-level cabinet shake-up, firing the country’s spy chief on Wednesday and, according to Western officials, lining up replacements for that post and the vacant Defense and Interior Ministries, at least one of which seemed likely to heighten tensions between Parliament and the presidential palace.

According to two Western officials, who spoke on the condition of anonymity because of the delicacy of the situation, top aides to Mr. Karzai recently told Western officials that Mr. Karzai intends to nominate a politically influential Tajik commander, Bismillah Khan Mohammadi, to take over the Defense Ministry — a move that is likely to provoke members of the Afghan Parliament who voted just three weeks ago to dismiss Mr. Mohammadi from his post as interior minister.

The officials said Karzai aides had informed Western officials that a powerful Karzai loyalist who has faced accusations of corruption and human rights abuses, Asadullah Khalid, was in line to take over the country’s main intelligence agency, and that a long-serving police official, Ghulam Mujtaba Patang, would lead the Interior Ministry.

One Western official, however, cautioned that there was still some chance that the names could be a trial balloon designed to elicit a reaction from American and NATO officials who still are in charge of providing most of the country’s security, or from Afghan lawmakers who must ratify the choices. Nothing is set in stone until Mr. Karzai makes a formal announcement, which could come as soon as Saturday, the official said. There were also signs on Wednesday that Mr. Mohammadi could face a tough vote in Parliament.