President Reagan said "phooey" yesterday to suggestions that he is undermining Central American peace prospects with his insistence on continued U.S. aid to the Nicaraguan rebels.

Delivering his weekly radio address from Camp David, Reagan reiterated that he will ask Congress in his State of the Union message Monday night to vote for financial aid to the contras, although he did not specify an amount.

"At stake here is whether Nicaragua becomes a Soviet base camp on the mainland of this hemisphere," the president said. "Imagine if the Sandinista vision of a communist Central America is realized and Mexico is threatened.

"The next vote on aid to the freedom fighters may be the most important this Congress casts," he said. "Some say if you're for aid to the freedom fighters in Nicaragua, you're against the peace process. Phooey!"

Asked yesterday whether any consideration is being given in the White House to a bid by some Democratic members of Congress to postpone submission of an aid request, spokesman Roman Popadiuk replied, "No decisions have been made on the actual level of the funding and on the final form of the package."

Rep. Lee H. Hamilton (Ind.), in the Democratic response, described the contra-aid issue as a choice between funding a war and supporting a peace process.