Amid reports the veteran Brazilian is keen to return and has the backing of sponsors, Sauber boss Kaltenborn earlier said “let’s see” when asked about the rumours.
But she told reporters on Saturday she only did not categorically rule out the 41-year-old for 2014 out of respect.
“I don’t think it is right that I just so abruptly say ‘No, we are not going to talk’,” said Kaltenborn.
But “I am ruling out that he would drive for us. Maybe it is better if one is that clear about it,” she added.
However, reports indicated McLaren is in fact concerned the tall German would tip its 2014 car over the minimum weight limit.
Hulkenberg admitted on Thursday he doesn’t think the British team is a “realistic option” for next year.
And team boss Martin Whitmarsh told Sky on Saturday: “I expect things to work out with Sergio. We’re not talking to Nico at the moment.”
Whitmarsh also told reporters to expect to hear news about high-profile recruitments in the Woking based team’s technical department, towards the end of a particularly bad season for McLaren.
“There are some as-yet unannounced (recruitments) that will be headline-grabbing when they get announced,” he said.