Rajapaksa's second term in office is due to begin in November 2010 after he won presidential polls in January. On a Supreme Court interpretation he is still serving the first term after calling early elections.
In the general elections this month several ministers lost their seats, including foreign minister Rohitha Bogollagama.
Amid intense horse trading among party seniors there is speculation that former trade minister Gamini Lakshman Peiris or human rights minister Mahinda Samarasinghe may get the foreign portfolio.
Finance will remain with President Rajapaksa. His brother Basil is tipped to get the tourism portfolio, political sources said.
Media reports Wednesday said another brother Chamal may be named the speaker of the new parliament.Rajapaksa has pledged to trim the cabinet to about 35 ministers after running his previous administration with more than a 100 ministers in an assembly of 225 members.