By Patricia Zengerle

WASHINGTON (Reuters) - Former President George H.W. Bush backs Mitt Romney for president, the Houston Chronicle reported on Thursday, an important boost for Romney from the Republican establishment less than two weeks before the Iowa caucuses.

The comments were not a formal endorsement but Bush told the newspaper he had known Romney for several years and also knew his father, former Michigan Governor George Romney.

"I think Romney is the best choice for us," Bush told the newspaper.

He cited Romney's "stability, experience, principles" and said, in a possible reference to Romney's famously volatile rival Newt Gingrich, "He's a fine person. I just think he's mature and reasonable - not a bomb thrower."

Romney, who has been a frontrunner in the race for the 2012 Republican nomination for months, is viewed as too moderate by many conservatives. He has failed to gain more than about 25 percent support in national polls as a series of rivals have surged into first place and then faded.

Gingrich pushed past Romney into first place recently, although the former speaker of the House of Representatives has faded partly due to withering attacks by Romney and his supporters.

Bush said he knew Gingrich fairly well and told the Chronicle, "I'm not his biggest advocate." The two men had a disagreement in 1990 when recession drove then-President Bush to agree to new taxes, despite having vowed not to do so. Gingrich, then a Republican House leader known for strong opinions and an outspoken style, declined to appear with the Republican president.

Bush lives in Texas but is not backing Texas Governor Rick Perry, who trails Romney in opinion polls. "I like Perry but he doesn't seem to be going anywhere; he's not surging forward," Bush said.

Perry succeeded Bush's son, George W. Bush, as Texas governor when the younger Bush became president in 2001. But Bush backed another Perry rival, U.S. Senator Kay Bailey Hutchison, over Perry in the Republican gubernatorial primary in 2010.

Bush said he could support any of the Republicans now seeking the nomination, although he expressed concern about the prospects for another Texan, the libertarian-leaning Congressman Ron Paul. Paul has moved past Gingrich in polls of Iowans likely to participate in the state's January 3 nominating caucuses.

"I want to see Obama beaten," Bush told the Chronicle. "I just don't believe Ron Paul can get the nomination."

(Reporting By Patricia Zengerle; Editing by Bill Trott)