The developed nations, led by the United States, must renounce any further backsliding toward trade protectionism. They should pledge to reduce remaining trade barriers against agricultural products and other goods of special importance to developing countries. The developing countries, meanwhile, should announce steps to open their markets further to manufactured products and services trade to stimulate growth and modernization. All participants should renew their commitment to conclude a comprehensive trade agreement at the World Trade Organization ministerial meeting later this year.

The world economy cannot recover without a rebound in trade, and trade cannot thrive if governments are raising tariff and non-tariff barriers. The most important task of G-20 leaders in Pittsburgh this week will be to return the global economy to the path of openness and expanding trade.

For Republicans, the chief opposition remains the faction of talk-radio-driven conservatives who just don't like immigration, period, especially when it comes from Latin America . For Democrats, who now run Washington , the chief opposition to allowing more foreign workers to enter the country legally is represented by organized labor.

As the Wall Street Journal reports this morning, advocates of immigration reform "worry that Democrats will defer to the AFL-CIO on the issue of legal immigration. The labor confederation has opposed a robust guest-worker program or higher levels of legal immigration, fearing they would depress wages. A larger labor presence would splinter the coalition of business and pro-immigration groups that embraced past immigration efforts, only to see them falter in the Senate."

As I've argued consistently in the past, immigration reform is not worth pursuing if it does not include expanding future flows of legal immigrants, both highly skilled and lower-skilled workers. If Congress confines itself to legalizing the 8 million or so workers already here illegally, with a vow to get tougher on enforcement, then we are just repeating the mistake of the 1986 Immigration Reform and Control Act.

We will know if President Obama and Democratic leaders in Congress are serious about fixing the problem of illegal immigration if they face down their labor-union allies and embrace a workable, market-oriented expansion of legal immigration. Otherwise, we are in for more futility, frustration and failure.