The Spain left-back is a target for both clubs and was asked about the speculation yesterday.
"It's too early to think about the future. I've only had two calls to the national team and the competition here is very high," said Alba.
"I just want to continue working to improve."
United are said to be watching Alba as quality cover for experienced left-back Patrice Evra. Their interest is known to Spanish FA officials, with Alba's interview coming via the federation's official website.