First the House passed a stopgap spending bill to keep the government funded beyond Monday. (Ping.)

But the Senate didn't like it. Now it's poised to pass an amended version by Saturday. (Pong.)

House Speaker John Boehner (R-Ohio) said Thursday the House won't simply sign off on the new bill. That means whatever changes the House makes would have to go back to the Senate for approval. (Ping.)

Welcome to the congressional budget debate, which is resembling a game of Ping-Pong days before the federal government is set for a partial shutdown if a new spending bill isn't signed by the end of Monday.

Gholi Soltani, at the near table, braces to return a table-tennis slam from Kye Kolar at Breadsoda in Glover Park. (Michael Temchine for The Washington Post)

The Senate is set to pass a bill that will strip out the portion of the House-passed measure that defunds Obamacare. The revamped bill will also include a new expiration date, Nov. 15.

Stripping out the defund provision will enrage House conservatives who fought for it. But it has long been clear that this would happen.

What isn't clear is what counter-changes Boehner will make to the eventual Senate-passed bill. He won't say.

The cast-iron conservatives in the House will demand that language aimed at shredding Obamacare be put back in. But House GOP leaders could be inclined to punt the Obamacare fight into next month's showdown over the debt ceiling.

Complicating matters even more, two hours after Boehner's announcement that the House would not sign off on the Senate bill as-is, Majority Leader Harry Reid (D-Nev.) said the Senate would not accept another House-passed funding resolution with different legislative strings attached to it.

Here's the reality: As in Ping-Pong, the legislative posturing will continue until one side doesn't hit the ball back to the other. The big question now is whether that will happen before or after the fast-approaching deadline for preventing a shutdown.

— Paul Kane contributed to this post