Gas estimation fail

Question

I am using remix and ganache and metamask and I encounter a confusing error. I compiled and deployed USDT at

0xdac17f958d2ee523a2206206994597c13d831ec7

on ganache with no problem. In order to do some test on it I wrote following contract in remix:

pragma solidity ^0.6.0;

import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/IERC20.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/SafeERC20.sol";

contract testTether {
    
    using SafeERC20 for IERC20;
    IERC20 public token;

    constructor(IERC20 _token) public {
        token = _token;
    }

    function transfer(address to, uint256 amount) public {
        token.safeTransfer(to, amount);
    }
}

when I try to call transfer function I get:

Gas estimation failed: Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending? Returned error: VM Exception while processing transaction: revert SafeERC20: low-level call failed

what is the problem?

Thanks in advance.