President Vladimir Putin has kept Russia guessing over his choice for prime minister, after sacking the entire government on Tuesday.
Kasyanov (left) plans to relax for a month or two to consider his future
He told the now ex-PM Mikhail Kasyanov and his ministers the change was aimed at forming a more efficient government.
A new prime minister must be named within two weeks, before the presidential election on 14 March.
Mr Putin has named Viktor Khristenko as interim prime minister but analysts do not expect him to stay after the poll.
Few names have been mentioned to replace Mr Kasyanov, but favourites for the post are Finance Minister Alexei Kudrin and Defence Minister Sergei Ivanov, according to reports in the Russian media.
Mr Kasyanov's cabinet continued work on a temporary basis.
Some observers said the sacking was intended to enliven the 14 March poll - which Mr Putin is expected to win by a landslide.
Mr Kasyanov was among the Kremlin's few survivors from the camp of Mr Putin's predecessor; his removal is seen as the Kremlin's formal break with the Yeltsin years.
On Wednesday, President Putin visited government headquarters in Moscow's White House, flanked by Mr Kasyanov and Mr Khristenko.
Visibly more relaxed than when announcing Mr Kasyanov's removal in a live television broadcast a day earlier, the president said he had chosen the change in the midst of the campaign for "political and administrative reasons".
If he had waited until after the poll, it would have been June before the new parliament approved a government, Mr Putin said.
He also promised to form a new government very soon.
"I am in a position to advise the public of the person I intend to present as prime minister. And I see this as my duty," Mr Putin said.
Later on Wednesday, he met lawmakers from the pro-Kremlin United Russia party, which holds a majority in the lower house of parliament - the State Duma - which must approve Mr Putin's nominee.
Russian news reports of the meeting did not indicate whether the president mentioned his choice by the name.
But the party's leader, Boris Gryzlov, was quoted by the Itar-Tass news agency as saying that "the consultations [on the issue] will probably continue this Sunday".
Under Russian law, the prime minister and his cabinet formally step down after a presidential election anyway, although all ministers can be reappointed.