Answer
The event leading up to and beginning the Tribulation is the signing of the seven-year covenant between Israel and the Antichrist. This event is found in Daniel 9:27 and Isaiah 28:14–22. It should be emphasized that it is not the Rapture that begins the Tribulation, but the signing of the seven-year covenant. Keeping this in mind will prevent many misunderstandings concerning the belief in the imminency of the Rapture. It is not the Rapture but the seven-year covenant that will begin the Tribulation.
The relationship of the Antichrist to the start of the Tribulation is found in Daniel 9:27: And he shall make a firm covenant with many for one week: and in the middle of the week he shall cause the sacrifice and the oblation to cease; and upon the wing of abominations shall come one that makes desolate; and even unto the full end, and that determined, shall wrath be poured out upon the desolate.
This verse is part of the famous Seventy Sevens Prophecy in Daniel 9. The entire context of this prophecy begins in verse 24 and continues through verse 27. According to verse 24, the prophecy states that a period of 490 years has been decreed over the people of Israel for the purpose of bringing to completion all history and prophecy. During the first sixty-nine sevens or 483 years, Jerusalem will be rebuilt. Verse 25 states that during this period, the people of Israel would experience troublesome times. At the end of the sixty-ninth seven, a gap suddenly enters the picture, for there is a break of time between the sixty-ninth and seventieth seven, during which three things will occur: first, the Messiah will be killed; secondly, Jerusalem and the Temple will be destroyed; and thirdly, a long period of desolation will follow. The first event occurred in A.D. 30, followed by the second event in A.D. 70. From A.D. 70, the Land lay in desolation and things began to change only when Israel again became a state in 1948. However, there is one more week of years to run, the seven years of the Great Tribulation. Verse 27 records the single event that will start the last seven years ticking away: the signing of the Seven-Year Covenant between the Antichrist and Israel. Therefore, one way that the Antichrist is involved with the beginning of the Tribulation is that the Tribulation cannot begin until he signs that seven-year covenant.
Extract from Dr Arnold Fruchtenbaum, Ariel Ministries Messianic Bible Study MBS038 'The Sequence of Pre-Tribulation Events' (San Antonio, TX.) pgs 32-33