The congressional budget impasse intensified yesterday as Senate conferees refused to bow to pressure from their House counterparts for some reduction in long-term spending authority for defense.

Failure to ease the 10-day deadlock, which is tying up billions of dollars' worth of emergency appropriations, prompted House Budget Committee Chairman Robert N. Giaimo (D-Conn.) to warn that "within another week the budget process will be irrelevant."

Pressure is mounting for bending the budget rules to permit prompt action on $15 billion in emergency spending for unemployment assistance, disaster relief and other politically sensitive programs. Congressional leaders have been holding firm, hoping to use the spending pressure as leverage to break the budget impasse, but they have warned they cannot hold off forever.

Giaimo has said that Congress might just as well scrap its 6-year-old budget control process if it begins granting waivers for spending programs because it cannot reach agreement on overall spending priorities within the confines of its nominally balanced budget for next year.

The stalemate began June 1 when the House rejected a defense-heavy $613.3 billion budget compromise for 1981 and then, in contradiction, insisted on keeping the same defense figures in any new compromise. The rejected plan had included $153.7 billion in outlays for defense and $171.3 billion in total military spending authority, which includes funds that would be committed but not necessarily spent during the year.

In an exchange of proposals yesterday, House conferees agreed to drop their earlier demand for some reduction in the defense outlay but sought a $1.8 billion cut in overall military spending authority. They also sought to increase transportation spending by $100 million by taking that amount from the razor-thin $500 million surplus that is proposed for the budget.

The Senate, however, refused to make any cuts in defense outlays or authority, while agreeing to take the $100 million from the surplus and increase long term spending authority for social programs by at least $800 million.

House budget strategists say that such a plan would go down to certain defeat in the House, where Democrats who are demanding cuts in military spending as well as increases in domestic outlays appear to hold the key to success for any budget plan.