WASHINGTON--A Reagan Administration official sent an unmistakable signal to Congress yesterday that the president intends to veto an $87.4-billion House appropriations bill, and Speaker Thomas P. O'Neill conceded Republicans have the votes to make the veto stick.

Referring to the president's threat last week to veto any "budget-busting" legislation, White House spokesman Larry Speakers said in a White House news conference, "This appears to be the kind of bill--which would provide funding for the departments of Labor, Education, and Health and Human Services--is $4 billion over the limits Congress set earlier this year.

O'Neill conceded there was "no question" the White House would sustain the 145 votes necessary to carry the veto. Earlier in the year, 155 Republican Congressmen sent a letter to the president pledging to support any veto, and the key vote on yesterday's bill was 249-168.