Richard E. Lyng, who has had close political ties to President Reagan for about 20 years, apparently has emerged as the front-runner among candidates to succeed John R. Block as secretary of agriculture.

Lyng, 67, who served as deputy secretary under Block until last year, met with White House staff this week, but refused to comment on the session except to say that he was "not seeking the job" and that he has had nothing to do with a farm-lobbyist campaign promoting his candidacy.

Asked if he would accept an administration offer, he said, "The fact is, I think almost anyone would accept if the president asked."

Although Lyng's background is not in farming, Washington insiders consider him a logical successor to Block because of his familiarity with farm programs and the USDA.

Block, announcing his resignation last week, speculated the White House would move quickly to fill the vacancy to assure continuity in management of the new farm-support legislation.

Administration sources indicated yesterday that an announcement might be slowed because the staff of Vice President Bush, apparently looking at the impact of farm policy on a 1988 presidential campaign, reportedly had become involved in the selection process.

Others mentioned as Block successors: U.S. Trade Representative Clayton S. Yeutter, who this week said he was not interested; Deputy Secretary John R. Norton, who has indicated he might leave his post because of economic reasons; Don Brock, a California farmer who worked in Reagan's last campaign, and Virginia farmer Robert Delano, departing president of the American Farm Bureau Federation, who is scheduled to meet with White House officials today.

Lyng was on the Reagan-Bush campaign team in 1980, then a year later was named deputy secretary with day-to-day USDA management duties. He left the department about a year ago to set up an agricultural consulting firm with William G. Lesher, another former USDA official.

Lyng, a Californian, was state agriculture director in the '60s when Reagan was governor. He was an assistant secretary of agriculture here from 1969 to 1973, then was the American Meat Institute's president until 1979.