Display api with Ionic

Good afternoon everyone, I'm consuming an api, but I can not display it in my template, it's being consumed, it appears on the console, but I can not get it in the template.

Component:

import { PaisesProvider } from './../../providers/paises/paises';
import { Component } from '@angular/core';
import { NavController } from 'ionic-angular';

@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})
export class HomePage {
  cotacao: string [];
  constructor(public navCtrl: NavController,
              private paisesProvider: PaisesProvider) {


  }

  ionViewDidLoad() {
    this.listaCotacao();  

  }

  listaCotacao() {
    this.paisesProvider.listaPaises()
    .subscribe(data => {
      this.cotacao = data;
      console.log(this.cotacao);

    });
  }
}

Template: 

<ion-header>
  <ion-navbar>
    <ion-title>Home</ion-title>
  </ion-navbar>
</ion-header>

<ion-content padding>

    <ion-item  *ngFor="let c of cotacao">
      Data : {{c.date}} Valor Compra {{c.buy}} Valor Venda {{c.sell}}    
    </ion-item>          

</ion-content>

The error appears:

  

Can not find a supporting object '[object Object]' of type   'object'. NgFor only supports binding to Iterables such as Arrays.