Washington ? Alan Greenspan, the nation’s economic guardian for 18 1/2 years, and his colleagues are poised to raise borrowing costs yet again at his final Federal Reserve meeting today.

The expected increase – intended to keep the economy and inflation on an even keel – will come as Greenspan ends his era at the central bank.

Greenspan, 79, plans to turn the reins over to his one-time Fed colleague Ben Bernanke, 52, who more recently has been chairman of President Bush’s Council of Economic Advisers. The Senate is expected to confirm Bernanke’s nomination today; his swearing-in as the new Fed chief likely will come Wednesday.

At today’s meeting, the Fed is expected to add one-quarter of a percentage point to an important short-term interest rate known as the federal funds rate. That would put the funds rate, the interest banks charge each other on overnight loans, at 4.50 percent.

In response, commercial banks would raise their prime lending rate – for certain credit cards, home equity lines of credit and other loans – by a corresponding amount to 7.50 percent.

Those moves would leave borrowing costs at their highest in more than 4 1/2 years.