Thread.Sleep() в переносимой библиотеке классов

В документах MSDN говорится, что Thread.Sleep() можно использовать в переносимой библиотеке классов. Компилятор говорит об обратном. Какие у меня есть альтернативы, кроме спин-петли? Thread.CurrentThread.Join() тоже не существует.

Файл проекта:

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
    <ProjectGuid>{C46B138E-CC30-4397-B326-8DD019E3874B}</ProjectGuid>
    <OutputType>Library</OutputType>
    <AppDesignerFolder>Properties</AppDesignerFolder>
    <RootNamespace>x0xtest.AVR</RootNamespace>
    <AssemblyName>x0xtest.AVR</AssemblyName>
    <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
    <TargetFrameworkProfile>Profile3</TargetFrameworkProfile>
    <FileAlignment>512</FileAlignment>
    <ProjectTypeGuids>{786C830F-07A1-408B-BD7F-6EE04809D6DB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
  </PropertyGroup>
  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
    <DebugSymbols>true</DebugSymbols>
    <DebugType>full</DebugType>
    <Optimize>false</Optimize>
    <OutputPath>bin\Debug\</OutputPath>
    <DefineConstants>DEBUG;TRACE</DefineConstants>
    <ErrorReport>prompt</ErrorReport>
    <WarningLevel>4</WarningLevel>
  </PropertyGroup>
  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
    <DebugType>pdbonly</DebugType>
    <Optimize>true</Optimize>
    <OutputPath>bin\Release\</OutputPath>
    <DefineConstants>TRACE</DefineConstants>
    <ErrorReport>prompt</ErrorReport>
    <WarningLevel>4</WarningLevel>
  </PropertyGroup>
  <ItemGroup>
    <Reference Include="System" />
    <Reference Include="System.Core" />
  </ItemGroup>
  <ItemGroup>
    <Compile Include="Attributes\AddressAttribute.cs" />
    <Compile Include="Attributes\RegAttribute.cs" />
    <Compile Include="Attributes\ROAttribute.cs" />
    <Compile Include="Attributes\RWAttribute.cs" />
    <Compile Include="Attributes\WOAttribute.cs" />
    <Compile Include="Devices\ATMega162.cs" />
    <Compile Include="Exceptions.cs" />
    <Compile Include="IntelHexFormat.cs" />
    <Compile Include="Properties\AssemblyInfo.cs" />
    <Compile Include="Proxy.cs" />
    <Compile Include="ProxyBase.cs" />
    <Compile Include="ProxyBase_UploadFirmware.cs" />
  </ItemGroup>
  <ItemGroup>
    <ProjectReference Include="..\x0xtest.Comm\x0xtest.Comm.csproj">
      <Project>{F78547AC-1CA1-4ADB-9FA8-3E7DEB682240}</Project>
      <Name>x0xtest.Comm</Name>
    </ProjectReference>
  </ItemGroup>
  <Import Project="$(MSBuildExtensionsPath32)\Microsoft\Portable\$(TargetFrameworkVersion)\Microsoft.Portable.CSharp.targets" />
  <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
       Other similar extension points exist, see Microsoft.Common.targets.
  <Target Name="BeforeBuild">
  </Target>
  <Target Name="AfterBuild">
  </Target>
  -->
</Project>