When Warren Buffett speaks, the investing world listens. So do economists, central bankers, and yes, even presidents. 

That's why it's a big deal that the Oracle of Omaha spoke out in a Fox Business interview on two huge issues in U.S. economic policy earlier this month. Here's what he had to say.

Don't raise interest rates in 2015
Ever since the Federal Reserve lowered its target federal funds to zero in December 2008, markets have speculated about when interest rates would begin to rise. More than six years later, that day has yet to arrive.

The consensus among most analysts is that the Fed will begin raising rates this year, perhaps in the summer or fall. Buffett thinks that move would be a challenge, if not impossible, to pull off.

He said that raising rates in 2015 "is going to be very tough ... when you've got what's going on around the world." 

To Buffett, the challenge in raising rates is not the strength of the U.S. economy, which is showing continuing improvement with every employment report, GDP estimate, and every look at the current levels of the Dow Jones and S&P 500 indices.

Instead, the problem is more about the interconnectedness of the global economy and the impact of a rise in U.S. rates on the rest of the world.

Buffet specifically mentioned Europe, which is currently in a rate-easing environment to try to avoid the region's third recession in the past few years. Rising rates in the U.S., coupled with low rates in Europe, would have the effect of making the dollar stronger relative to the euro. Buffett didn't mention Japan, but the situation there is largely the same. Even China is seeing its once unstoppable double-digit GDP growth slow.

An even stronger dollar will exacerbate these global growth issues even further. A study from Bank of America's Merrill Lynch predicts that global nominal GDP will shrink 3.5% in 2015, largely driven by a strengthened dollar.

The "not-in-my-backyard" problem
Buffett then shifted gears, repeating a call for the federal government to approve the much-debated Keystone XL pipeline. This pipeline would facilitate the transport of Canadian-drilled oil to U.S.-based refiners and shipping networks.   

In an interview on CNBC in March of last year, Buffett stated that he'd "vote yes" on the project if he were a D.C. lawmaker. His opinion hasn't changed, saying this month that "by and large, Keystone should be done." 

For Buffett, the viewpoint is based on a bigger-picture perspective of what's best for the United States. The Burlington Northern Santa Fe Railway, owned by Berkshire Hathaway (NYSE:BRK-A) (NYSE:BRK-B), would actually lose business with the pipeline, as much of that oil is shipped by rail today.

The challenge is that getting the pipeline approved is characterized by what Buffett calls a "not-in-my-backyard" problem. Areas where the pipeline would be built are cautious, given the thought of having hundreds of millions of gallons of oil rush through neighborhoods, and past schools, farms, and waterways. The risk of a major spill is terrifying for communities that would suffer the potential environmental and economic fallout from such a disaster. 

Yet, many of those risks already exist by transporting the product on railroads. Some argue that the pipeline would decrease the chance of a disaster overall. It would also lower costs in the supply chain of oil products, giving North America oil an advantage on international markets. To Buffett, the improvements to the oil infrastructure are worth the risks and costs of building the Keystone.

Will rates rise in 2015? Will the Keystone XL pipeline ever get built? The answers to those questions can only be answered with time. In the meantime, though, it's always a learning experience listening to the Oracle of Omaha discuss the issues facing the national and global economy today.