Updated: 7:37 p.m.
Last week's standoff between Sen. Rand Paul (R-Ky.) and Majority Leader Harry Reid (D-Nev.) that threatened to wreak havoc on the Senate schedule appears set to be reprised this week, as lawmakers try to head for the exits.
The next chapter could delay - though by no means imperil - passage of a continuing resolution to keep the government funded for the next six months.
In a "Dear Colleague" letter sent late today, Paul sought support for his effort to have the Senate vote on cutting off aid to Pakistan, Egypt and Libya.
Reid has resisted allowing the votes, often saying the matter is not related to the pending floor business.
Paul says he will filibuster any effort to expedite Senate business until he secures the votes. That could delay the Senate's departure until the coming weekend because it is not scheduled to hold a cloture vote on taking up the six-month stopgap spending package until Wednesday.
If Reid and Paul remain at loggerheads, the timeline for finishing the CR could be pushed as late as Sunday. The measure itself is not in jeopardy; it got through the House easily last week, 329-91.
"We must demand accountability from the government of Pakistan, which receives over $3 billion from us every year yet routinely plays both sides of some of the most important issues while openly thwarting our objectives in the region," Paul said.
Paul is pressing for the release from Pakistani custody of Dr. Shakil Afridi, who helped U.S. forces track down and ultimately kill Osama bin Laden.
Critics of Paul's proposal argue that Congress should not take any action that risks further destabilizing Pakistan.
Paul also wants to curb or eliminate aid to Egypt and Libya after security was compromised at State Department facilities in those countries last week.
"We must take steps to cut foreign aid to Egypt and Libya - or any other country which fails to secure our embassies - and we must make it clear that, unless there is full cooperation in bringing these attackers to justice, no foreign aid will be provided in the future," Paul wrote in the letter. "A full investigation is necessary to determine who is responsible for these murders, and simply identifying the persons responsible is not enough."
Paul is also seeking support from House Members.
The Obama administration is moving in the opposite direction, pushing for an economic package to support Egypt. State Department spokeswoman Victoria Nuland said Monday that Secretary of State Hillary Rodham Clinton would push Congress for assistance on that front this week.
"We think it is absolutely essential that we support those forces in Egypt who want to build a peaceful, stable, democratic country, with prosperity restored, jobs for people, et cetera. And that's what the assistance that the president has pledged and that we are working with the Hill on is for," Nuland said.
Senior administration officials will be on the Hill this week to brief lawmakers on the security challenges in the Middle East as the investigation continues into last week's events, including the killing of four Americans at a U.S. consulate in Benghazi, Libya. The Senate Foreign Relations Committee has a closed briefing planned for Thursday morning.
This is not the first time Paul has tried to filibuster a bill over the Pakistan amendment. However, Reid has blocked his attempts using procedural maneuvers. Paul tried to get a vote on a Pakistan aid amendment during the June debate on the Senate's farm bill, but Reid stopped that as well.
Some Senators - such as Senate Armed Services Chairman Carl Levin (D-Mich.) - have questioned the wisdom of not only Paul's proposal but also of voting on it without a full debate on Pakistan.
Plus, there is the danger that foreign policy votes could be misinterpreted both at home and abroad.
Last week, Sen. Lindsey Graham (S.C.), the GOP's top foreign aid appropriator, blasted Paul's amendment.
"Pakistan is a country with nuclear weapons that is hanging by a thread. I think it would be a very bad idea," Graham said of cutting off aid.
He added that aid should have some conditions but said he was "worried about the possibility of a nuclear-armed Pakistan falling into extremist hands. ... Now is not the time to disengage."