Sen. Barack Obama, the presumptive Democratic presidential nominee, told an enthusiastic House Democratic caucus Tuesday that Democrats can win in November if they remember that the American people want responsible change and propose ways to deliver it.

“Every member of Congress recognizes the historic challenges and the historic opportunities this election is,’’ Obama said, surrounded by House Democratic leaders, after the meeting in the Cannon Caucus Room. He said he told those of the 236-member House caucus who attended that the party must emphasize, “Not larger government, but responsible government, honest government and efficient government.’’

Obama’s visit to the House side of Capitol Hill capped a busy day in Washington for the prospective Democratic presidential nominee. He also met with President Bush’s Treasury Secretary Henry M. Paulson Jr., and Federal Reserve Chairman Ben Bernanke to discuss economic issues and with visiting Pakistani Prime Minister Yousuf Raza Gilani to talk about fighting the Taliban in Pakistan’s tribal regions and Afghanistan and Al Qaeda.

More than just a pep talk to a group of Democrats, who are pretty upbeat about their election prospects, Obama’s caucus appearance was an opportunity for members to ask their prospective nominee questions. He fielded about a dozen questions on a wide variety of domestic and foreign policy topics, participants said.

Highlights included Obama’s statement that if Iran thinks it can get a better deal on its nuclear program from the United States and its international partners by waiting for a new president it is mistaken. Obama, just back from a foreign trip that included stops in Israel and the Palestinian territories, reiterated that he thinks the United States has a vested interest in pushing for an Israeli-Palestinian peace accord.

He also said the United States has to invest more in its physical infrastructure and has to be fiscally disciplined to revive the economy.

Several of those in the room said Rep. Adam B. Schiff, D-Calif., met scattered boos when he suggested to Obama that if elected president the senator appoint a bipartisan cabinet that would include Robert Gates, the current defense secretary, staying on in that post. Schiff wouldn’t comment after the meeting.

Even though they were behind closed doors, Obama chose not to get too specific on any issue. Joseph Crowley, D-N.Y., said Obama told the caucus, “I don’t want to jinx myself” by getting too specific about what he would do next year if he is elected over the probable Republican nominee, Sen. John McCain. “I’m not going to talk about that kind of thing until I actually get there,” Crowley said Obama added.

Democratic Senate and House campaign leaders, who expect the party to pick up seats in both houses in November, are warning Democrats against over-confidence as they head into the fall campaign. Christopher Carney, D-Pa., said Democrats aren’t overconfident.

“Most people in the caucus are pretty smart. They read the polls, They see what’s ahead. And I think Senator Obama knows he’s got a lot of work ahead of him. This is not put away by any means,” Carney said.

John B. Larson, D-Conn., vice chair of the caucus, said the reason the party is so optimistic about Obama’s prospects to capture the White House is that “he’s a hope monger. He just exudes hope.’’

Donna Edwards of Maryland, the Democrats’ newest member said, “It was a wonderful experience. It was an opportunity for us as a caucus to show how unified we are behind his candidacy whether we represent red or blue states.”

Republicans welcomed Obama to the caucus by trying to put part of the blame for high gasoline prices on his shoulders, along with the refusal by Speaker Nancy Pelosi, D-Calif., and Senate Majority Leader Harry Reid, D-Nev., to allow a vote on the GOP’s proposals to boost offshore oil drilling.

“He should scrap his agenda and instead call on his colleagues to hold an up or down vote’’ on drilling proposals, said Rep. Adam H. Putnam, R-Fla, head of the House Republican Conference.

Saying that many Democrats are prepared to vote for such legislation, he added, “Only three people stand in the way -- Obama, Pelosi and Reid.’’

Republicans in both houses are pushing for a vote on their energy proposals before the Congress leaves for its long August recess.

Those at the caucus said Obama called for an energy policy that concentrates on new sources and on more drilling. But Democrats say some 83 million acres of government land and offshore acreage is already available for drilling and hasn’t been utilized by oil and gas companies.

Jonathan Allen and Michael Teitelbaum contributed to this story.