If one partner has totally switched off, no intimacy, nothing, then that probably means you have bigger problems, or that you aren't compatible.
Similarly, if one partner makes it obvious that they're unsatisfied then the other will feel pressure and there is no bigger turn off than pressure. The stronger the pressure the worse it will be, unless it's verging on forceful/abusive in which case the pressured partner is more likely to give in, however, that's an awful prospect - having sex because you feel there is no other option - and really not conducive in any way to a healthy relationship.
If you're sure you're not in either of these scenarios then it's worth sitting down and properly talking about it, but actually avoiding the subject of sex itself. I know that sounds counter-intuitive, but it isn't - the problem when you have a situation like this is that one person gets it in their head "I need more sex" and the other gets it in their head "I need less sex/I don't want to have more sex/I don't like sex" when actually it's not necessarily about sex at all.
So, the HSD (higher sex drive) partner needs to work out what it actually is that they want that they think sex will provide - whether that's intimacy, connection, shared physical experience, stress release, whatever. Then consider whether it's fair to rely on their partner for those needs (e.g. stress release - no, physical sexual pleasure - no, at least not all the time, ie don't hold them responsible for your lack of sexual release if they don't want it at a particular time)
The ones which do necessarily require the LSD partner to be involved like connection, intimacy etc, hold on to those for a minute.
The LSD partner needs to do a similar thing, ie think about what it is they find off-putting about sex and write all that down, e.g. fear of pregnancy, physical exertion, pain, invasion of personal space, worry that "smaller" interactions e.g. kissing etc will lead to more, body/self esteem worries, general feeling of not enough going on elsewhere in the relationship.
If you can both be honest and be prepared for the other's thoughts to perhaps be hurtful it will help much more in the long run. Anyway, once you both have your thoughts/feelings around sex without it being about sex overtly you can perhaps talk and find ways to meet the HSD's needs without triggering the LSD's discomfort. For example, you could perhaps have less penetrative sex and concentrate on other things more with penetrative sex more of an occasional thing. You could find non-sexual ways of being intimate like having a bath together or taking up massage. You could start a new hobby together or take on a project, or look at your everyday routines - perhaps you've fallen into a pattern of doing your own thing, or you could fit in a time to sit and connect, perhaps first thing in the morning with a coffee or designate one night a week as a "date night" (not intending to lead to sex, but could if it happens to go there) etc etc.
The hope with all of this is that it does any or all of three things, firstly that it reduces the HSD's need for sex because the needs are getting met in other ways, that it creates a more open atmosphere for talking about sex so that the HSD can reassure the LSD that they are loved, appreciated and respected and that it's fine if they don't want to do something or if they start but don't finish etc and the LSD can reassure the HSD that it's not them they are rejecting. And also that the LSD feels closer to the HSD which perhaps will lead to more sex or more sexual/intimate activity.