NEW YORK (AP) — Home prices in April rose for the first time in seven months as government tax credits bolstered the housing market. But the rebound may be short-lived now that the incentives have expired.

The Standard & Poor’s/Case-Shiller 20-city home price index released Tuesday posted an 0.8 percent gain. It had fallen in each of the past six months.

Eighteen of 20 cities showed price increases in April from March. Washington, San Francisco and Dallas each posted gains of 2 percent or more. Eleven cities reversed their declines from the month before.

Only Miami and New York recorded price declines. New York hit a new low for the index.

Nationally, prices have risen 3.8 percent from their April 2009 bottom. But they remain 30 percent below their July 2006 peak

The overall price gains highlight the impact of the federal tax credits for homebuyers. Buyers rushed to purchase before the tax credits expired at the end of April. The numbers are likely to drop in the next report.

“Other housing data confirm the large impact, and likely near-future pullback, of the federal program,” said David M. Blitzer, S&P’s index chairman.

Last week, the government reported that new home sales fell in May to their lowest level on record, plunging 33 percent from the month before. And sales of previously occupied homes edged down 2.2 percent.

Also, homebuilders KB Home and Lennar Corp. both reported sharp declines in new home orders in the three months ended in May.