His comments, at his first post-cabinet meeting news conference since taking office last December, came a day after the European Central Bank signaled it was preparing to buy Spanish and Italian bonds but only after EU bailout funds were triggered and countries had asked for help.
A source said separately that Spain would not decide whether to apply for several weeks.
Buying bonds and providing aid would all be designed to bring down what have been prohibitive borrowing costs in the indebted countries.
Rajoy said he was ready to do what is best for Spain, going far further than he did on Thursday when, during a press appearance with Italian Prime Minister Mario Monti, Rajoy three times declined to say whether he would seek the aid.
"I will do, as I always do, what I believe to be in the best interest of the Spanish people," Rajoy said on Friday.
"We still don't know what these measures are," he said, reference to a comment by ECB President Mario Draghi that the bank was examining non-conventional measures to defend the euro.
"What I want to know is what these measures are, what they mean and whether they are appropriate and, in light of the circumstances, we will make a decision, but I have still not taken any decision," he said.