lightning navigation pass parameters in URL

on my custom community page, using a Lighting web component and navigating to a different page by passing some query string in URL, problem is the unable to refer Javascript variable in below code snippet:

let keyVal;
let val;
// here this.params is having a value like "tabset=e2571"

if(this.params && this.params.split('=').length === 2){
  keyVal = this.params.split('=')[0];
  val = this.params.split('=')[1];
}

this[NavigationMixin.Navigate]({
  type: 'comm__namedPage',
  attributes: {
    pageName: 'samplePage'

  },
  state: {
    keyVal : val
  }
});

This code is not able to refer the value of keyVal variable and ended up to generate below URL: Actual URL: https://xxxx.cs151.force.com/xxxxx/s/samplePage?keyVal=e2571

Expected URL https://xxxx.cs151.force.com/xxxxx/s/samplePage?tabset=e2571

I have already tried with replacing the variable name with c__keyVal but no luck.