The Detroit News, this city's largest circulation newspaper, agreed late this afternoon to print its rival, the Detroit Free Press, after the Free Press was shut down Saturday by an unexpected Teamsters strike.

In an unusual agreement between the city's intensely competitive daily newspapers, News Vice President Robert C. Nelson said that his paper "will print both the News and the Free Press and will continue to do so for the duration of the strike."

The planning for Monday called for a one section, 16-page edition of the Free Press.

It was unclear late yesterday whether the Teamsters' striking circulation drivers also would strike the News once press runs began on the Free Press. The circulation drivers at both newspapers are members of Local 372, although the News employes ratified the same contract the Free Press drivers rejected.

"The folks at the News are obviously willing to take the risks," said Dave Lawrence, executive editor of the Free Press. "Obviously, these folks [the union] are trying to whip other folks around. That's what they're trying to do."

Ed Schribner, president of the local, called for the agreement between the two papers "remarkable" and said "we're going to have to take a look at" whether the union would request drivers at the News to walk out as well.

The strike vote Saturday hit the Free Press just as the paper was gearing up for its elaborate and expensive coverage of the Republican convention here. uThe paper had invested hundreds of thousands of dollars in the convention coverage, and had planned a special 56-page convention supplement.

The Free Press had commissioned "Doonesbury" cartoonist Garry Trudeau to draw convention cartoons for the paper, hired nationally known columist Richard Reeves for daily commentary and brought in comic Mark Russell for a joke of the day.

The strike also left Free Press reporters, some who said they had never before covered a national convention, angry, frustrated and wondering what their own union, the Newspaper Guild, would do during this strike.

"The guild is not on strike, but the guild will not cross picket lines," said guild Vice President Joyce Walker-Tyson, a Free Press convention reporter.

The only picket lines last night were around the Free Press offices on Lafayette Street, and around the printing plant on the Detroit waterfront. Because there were no pickets at Cobo Hall, site of the GOP convention that opens Monday, reporters continued to work there even though they had no paper to print their stories.

Walker-Tyson said that if the drivers decided to strike the News for printing the Free Press, the guild would honor that picket line.

The last time the Free Press shut down was during a bitter, nine-month labor dispute in 1968. The unions that year first struck the Detroit News, and the Free Press locked out its own employes and voluntarily closed down in a show of publishers' solidarity.

Neslon, the News' vice president and general manager, said Saturday that the publishers had no such agreement to close down in the event unions struck one or the other paper.